Magnetic recording cartridge

ABSTRACT

A magnetic recording cartridge is provided and including a magnetic recording medium, wherein an average thickness of the magnetic recording medium tT is 3.5 μm≤tT≤5.6 μm, a dimensional change amount Δw in a width direction of the magnetic recording medium with respect to a tension change in a longitudinal direction of the magnetic recording medium is 700 ppm/N≤Δw≤20000 ppm, and the magnetic recording medium is accommodated in a state of being wound around the reel in the cartridge case and (a servo track width on an inner side of winding of the magnetic recording medium)−(a servo track width on an outer side of winding of the magnetic recording medium)&gt;0 is satisfied.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/502,418, filed on Jul. 3, 2019, which application claims the benefitof Japanese Priority Patent Application JP 2019-086717 filed on Apr. 26,2019, the entire contents of which are incorporated herein by reference.

BACKGROUND Technical Field

The present technology relates to a magnetic recording cartridge.

Background Art

In recent years, in magnetic tapes (magnetic recording mediums) used asdata storage for computers, a track width and a distance betweenadjacent tracks have become very narrow in order to improve a recordingdensity of data. Thus, when the track width and the distance between thetracks are narrow as described above, a maximum allowable change amountas a dimensional change amount of a tape itself due to environmentalfactors such as, for example, a change or the like in temperature andhumidity becomes small.

Several technologies for reducing the dimensional change amount havebeen proposed so far. For example, in the magnetic tape medium disclosedin PTL 1 below, in a case where a Young's modulus of a nonmagneticsupport in a width direction is X and a Young's modulus of a back layerin the width direction is Y, X×Y is 6×10⁵ or more if X is 850 kg/mm² orgreater or less than 850 kg/mm² and Y/Z is 6.0 or less when a Young'smodulus of a layer in the width direction including a magnetic layer isZ.

CITATION LIST Patent Literature PTL 1

JP 2005-332510A

SUMMARY Technical Problem

It is desirable to provide a magnetic recording cartridge including amagnetic recording medium capable of suppressing a dimensional change ina width direction by adjusting tension applied in a longitudinaldirection of a tape.

Solution to Problem

According to an embodiment of the present technology, there is provideda magnetic recording cartridge including a magnetic recording medium ofwhich

an average thickness t_(T) is t_(T)≤5.6 μm,

a dimensional change amount Δw in a width direction with respect to atension change in a longitudinal direction is 660 ppm/N≤Δw, and

a squareness ratio in a vertical direction is 65% or more,

in which the magnetic recording medium is accommodated in a state ofbeing wound around a reel and (a servo track width on an inner side ofwinding of the magnetic recording medium)−(a servo track width on anouter side of winding of the magnetic recording medium)>0 is satisfied.

The magnetic recording medium may have a servo track width larger than aservo read head width of a magnetic recording and reproducing apparatusin which the magnetic recording cartridge is loaded.

The magnetic recording and reproducing apparatus may be a timing servotype magnetic recording and reproducing apparatus.

The dimensional change amount Δw may be 700 ppm/N≤Δw.

The dimensional change amount Δw may be 750 ppm/N≤Δw.

The dimensional change amount Δw may be 800 ppm/N≤Δw.

The magnetic recording medium may include a back layer, and a surfaceroughness R_(ab) of the back layer may be 3.0 nm≤R_(ab)≤7.5 nm.

The magnetic recording medium may include a magnetic layer and a backlayer, and a friction coefficient μ between a surface on a side of themagnetic layer and a surface on a side of the back layer may be0.20≤μ≤0.80.

A thermal expansion coefficient α of the magnetic recording medium maybe 5.5 ppm/° C.≤α≤9 ppm/° C. and a humidity expansion coefficient β ofthe magnetic recording medium may be β≤5.5 ppm/% RH.

A Poisson's ratio ρ of the magnetic recording medium may be 0.25≤ρ.

An elastic limit value σ_(MD) of the magnetic recording medium in thelongitudinal direction may be 0.7 N≤σ_(MD).

The elastic limit value amp may not depend on a speed V when elasticlimit is measured.

The magnetic recording medium may include a magnetic layer, and themagnetic layer may be vertically aligned.

The magnetic recording medium may include a back layer and an averagethickness t_(b) of the back layer may be t_(b)≤0.6 μm.

According to another embodiment of the present technology, the magneticrecording medium may include a magnetic layer, and the magnetic layermay be a sputtered layer.

In a case where the magnetic layer is a sputtered layer, an averagethickness t_(m) of the magnetic layer may be 9 nm≤t_(m)≤90 nm.

According to still another embodiment of the present technology, themagnetic recording medium may include a magnetic layer, and the magneticlayer may contain magnetic powder.

In a case where the magnetic layer contains magnetic powder, the averagethickness t_(m) of the magnetic layer may be 35 nm≤t_(m)≤90 nm.

The magnetic powder may include c iron oxide magnetic powder, bariumferrite magnetic powder, cobalt ferrite magnetic powder, or strontiumferrite magnetic powder.

Furthermore, according to further embodiment of the present technology,there is provided a magnetic recording cartridge including a magneticrecording medium of which

an average thickness t_(T) is t_(T)≤5.6 μm,

a dimensional change amount Δw in a width direction with respect to achange in tension in a longitudinal direction is 660 ppm/N≤Δw, and

a squareness ratio in a vertical direction is 65% or more,

in which the magnetic recording medium has a servo track width largerthan a servo read head width of a magnetic recording and reproducingapparatus in which the magnetic recording cartridge is loaded.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a schematic view of an example of a magnetic recordingcartridge according to an embodiment of the present technology.

FIG. 1B is a cross-sectional view showing an example of a configurationof a magnetic recording medium included in a magnetic recordingcartridge according to an embodiment of the present technology.

FIG. 2 is a cross-sectional view showing a configuration of a magneticparticle.

FIG. 3A is a perspective view showing a configuration of a measurementdevice.

FIG. 3B is a schematic view showing the details of a measurement device.

FIG. 4 is a graph showing an example of an SFD curve.

FIG. 5 is a schematic view showing a configuration of a recording andreproducing apparatus.

FIG. 6 is a cross-sectional view showing a configuration of a magneticparticle in a modification.

FIG. 7 is a cross-sectional view showing a configuration of a magneticrecording medium in a modification.

FIG. 8 is a cross-sectional view showing another example of aconfiguration of a magnetic recording medium included in a magneticrecording cartridge according to an embodiment of the presenttechnology.

FIG. 9 is a schematic view showing a configuration of a sputteringapparatus.

FIG. 10 is a cross-sectional view showing another example of aconfiguration of a magnetic recording medium included in a magneticrecording cartridge according to an embodiment of the presenttechnology.

FIG. 11 is a schematic view showing measurement positions of a deviationamount of a servo track width.

FIGS. 12A to 12C are a schematic views showing a method of measuring adeviation amount of a servo track width.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments for implementing the presenttechnology will be described. Note that the embodiments described belowshow representative embodiments of the present technology, and the scopeof the present technology is not limited to only these embodiments.

The present technology will be described in the following order.

1. Description of the present technology

2. First embodiment (example of magnetic recording cartridge Includingcoating type magnetic recording medium)

-   -   (1) Configuration of magnetic recording cartridge    -   (2) Description of each layer    -   (3) Physical properties and structure    -   (4) Method of manufacturing magnetic recording medium    -   (5) Recording and reproducing apparatus    -   (6) Effect    -   (7) Modification

3. Second embodiment (example of magnetic recording cartridge includingvacuum thin film type magnetic recording medium)

-   -   (1) Configuration of magnetic recording cartridge    -   (2) Description of each layer    -   (3) Physical properties and structure    -   (4) Configuration of sputtering apparatus    -   (5) Method of manufacturing magnetic recording medium    -   (6) Effect    -   (7) Modification    -   (8) Other examples of magnetic recording media

4. Example

1. DESCRIPTION OF THE PRESENT TECHNOLOGY

There is a need to further increase a recording capacity per magneticrecording cartridge. For example, in order to increase the recordingcapacity, it is conceivable to increase a tape length per magneticrecording cartridge by reducing a thickness of a magnetic recordingmedium (e.g., a magnetic recording tape) included in the magneticrecording cartridge (reducing an overall thickness).

However, as the magnetic recording medium becomes thinner, a dimensionalchange may occur in a track width direction. The dimensional change inthe width direction may cause an undesirable phenomenon for magneticrecording, such as, for example, an off-track phenomenon, etc. Theoff-track phenomenon refers to a situation in which a target track isnot present at a track position for a magnetic head to read or asituation in which the magnetic head reads a wrong track position.

In the past, in order to suppress the dimensional change of the magneticrecording medium, for example, a method of adding a layer forsuppressing the dimensional change of the magnetic recording medium orthe like is performed.

However, the addition of the layer may increase a thickness of themagnetic recording tape and does not increase a tape length percartridge product.

The inventors of the present technology are examining a magneticrecording medium suitable for use in a recording and reproducingapparatus, whose width may be kept constant or substantially constant byadjusting tension of the long-shaped magnetic recording medium in alongitudinal direction. The recording and reproducing apparatus detects,for example, dimensions or a dimensional change in the width directionof the magnetic recording medium, and adjusts tension in thelongitudinal direction on the basis of a detection result.

However, in the magnetic recording medium suppressed in the dimensionalchange, the dimensional change amount in the width direction based onthe change in tension in the longitudinal direction is small. Therefore,it is difficult to keep the width of the magnetic recording mediumconstant or substantially constant even though tension is adjusted inthe longitudinal direction by the recording and reproducing apparatus.

In consideration of the above circumferences, the present inventorsexamined a magnetic recording cartridge having a high recording capacityper cartridge. As a result, the present inventors have found that amagnetic recording cartridge having a specific configuration has a highrecording capacity and is suitable for use in a recording andreproducing apparatus which adjusts tension in the longitudinaldirection.

Furthermore, the tension adjustment may cause a phenomenon peculiar tothe tension adjustment, such as wrinkles when the magnetic recordingmedium is wound around a reel. The phenomenon may occur especially in acase where the tension loosens. The present inventors have also foundthat the occurrence of the phenomenon may be prevented by a magneticrecording cartridge having a specific configuration.

In other words, the present technology provides a magnetic recordingcartridge including a magnetic recording medium in which an averagethickness t_(T) is t_(T)≤5.6 μm, a dimensional change amount Δw in awidth direction with respect to a change in tension in a longitudinaldirection is 660 ppm/N≤Δw, and a squareness ratio in a verticaldirection is 65% or more. The magnetic recording medium is accommodatedin the magnetic recording cartridge in a state where the magneticrecording medium is wound around a reel, and (servo track width on innerside of winding of magnetic recording medium)−(servo track width onouter side of winding of magnetic recording medium)>0 is satisfied.

An average thickness t_(T) of the magnetic recording medium included inthe magnetic recording cartridge according to the embodiment of thepresent technology may be 5.6 μm or less, preferably 5.5 μm or less,more preferably 5.3 μm or less, and still more preferably 5.2 μm orless, 5.0 μm or less, or 4.6 μm or less. Because the magnetic recordingmedium is so thin, for example, the length of the tape wound up in onemagnetic recording cartridge can be longer, thereby increasing arecording capacity per magnetic recording cartridge.

In the magnetic recording medium included in the magnetic recordingcartridge according to the embodiment of the present technology, thedimensional change amount Δw in the width direction with respect to thechange in tension in the longitudinal direction is 660 ppm/N or more,more preferably 670 ppm/N or more, and still more preferably 700 ppm/Nor more, 710 ppm/N or more, 730 ppm/N or more, 750 ppm/N or more, 780ppm/N or more, or 800 ppm/N or more. The fact that the magneticrecording medium has the dimensional change amount Δw within the abovenumerical range contributes to making it possible to maintain the widthof the magnetic recording medium at a constant level by adjustingtension of the magnetic recording medium in the longitudinal direction.

Furthermore, an upper limit of the dimensional change amount Δw is notparticularly limited, and may be, for example, 1700000 ppm/N or less,preferably 20000 ppm/N or less, more preferably 8000 ppm/N or less,still more preferably 5000 ppm/N or less, 4000 ppm/N or less, 3000 ppm/Nor less, or 2000 ppm/N or less. In a case where the dimensional changeamount Δw is too large, it may be difficult to stably run in themanufacturing process.

A method of measuring the dimensional change amount Δw will be describedin (3) of 2. below.

The magnetic recording medium included in the magnetic recordingcartridge according to the embodiment of the present technology has asquareness ratio in the vertical direction of 65% or more, preferably70% or more, more preferably 73% or more, and still more preferably 80%or more. Because the magnetic recording medium has a squareness ratio S2within the above numerical range, more excellent electromagneticconversion characteristic may be obtained. Furthermore, a servo signalshape is improved, making it easier to control a drive side.

A method of measuring a squareness ratio in the vertical direction willbe described in (3) of 2. below.

As described above, the magnetic recording medium included in themagnetic recording cartridge according to the embodiment of the presenttechnology is thin, suitable for a recording and reproducing apparatusthat adjusts tension in the longitudinal direction, and is excellent inelectromagnetic conversion characteristic, and thus, a recordingcapacity per magnetic recording cartridge may be significantlyincreased.

Moreover, the magnetic recording cartridge according to the embodimentof the present technology includes the magnetic recording medium in astate of being wound around a reel, and (servo track width on inner sideof winding of magnetic recording medium)−(servo track width on outerside of winding of magnetic recording medium)>0 μm is satisfied.Hereinafter, in the present specification, (servo track width on innerside of winding of magnetic recording medium)−(servo track width onouter side of winding of magnetic recording medium) is also referred toas “difference between servo track widths of the inner side and theouter side of the winding”. The difference between the servo trackwidths on the inner side of the winding and the outer side of thewinding is preferably 0.01 μm or more, more preferably 0.02 μm or more,and still more preferably 0.05 μm or more. The difference between servotrack widths on the inner side of the winding and the outer side of thewinding may be, for example, 0.10 μm or more, 0.15 μm or more, or 0.20μm or more. When the difference between the servo track widths of theinner side of the winding and the outer side of the winding is withinthe above numerical range, the occurrence of wrinkles in the magneticrecording medium (in particular, a portion of the magnetic recordingmedium closer to the reel) wound around the reel in the cartridge can beprevented. The wrinkles may cause, for example, winding deviation, trackdeviation, or the like, during running, and the occurrence of thesephenomena due to the wrinkles can also be prevented by the presenttechnology. A method of measuring the difference and a method ofmeasuring a deviation amount of the servo track width used to calculatethe difference will be described in (3) of 2. below.

Suppression of the occurrence of wrinkles will be described in moredetail below.

The recording and reproducing apparatus capable of keeping the width ofthe magnetic recording medium constant or substantially constant byadjusting tension of the long-shaped magnetic recording medium in thelongitudinal direction adjusts the tension in the longitudinal directionaccording to, for example, servo track widths. For example, in a casewhere the servo track width is wider than a predetermined width, theapparatus increases tension in the longitudinal direction to keep theservo track width constant, and in a case where the servo track width isnarrower than the predetermined width, the apparatus decreases thetension in the longitudinal tension to keep the servo track widthconstant. In this manner, the width of the magnetic recording medium iskept constant.

When a difference between the servo track widths of the inner and outersides of winding is a negative value, it means that the servo trackwidth of the inner side of the winding is narrower than that of theouter side of the winding. In a case where the difference is a negativevalue, for example, a servo track width having the narrowest portion ispresent within a half region of an end portion (hereinafter, alsoreferred to as a “reel-connected end portion”) of the magnetic recordingmedium connected to a reel of the magnetic recording cartridge, that is,the servo track width of a region near the reel-connected end portion isnarrower than a servo track width of a region near the opposite endportion (hereinafter, also referred to as an “outer end portion”).Therefore, in a case where the magnetic recording medium is wound aroundthe reel in the magnetic recording cartridge, a longitudinal tensionapplied to winding in the region near the reel-connected end portion isweaker and a longitudinal tension applied to winding in the region nearthe outer end portion is stronger to keep the servo track widthconstant. As a result, the region of the magnetic recording medium nearthe reel-connected end portion is wound around the reel with a weakertension than the region thereof near the outer end portion. When themagnetic recording medium is wound in this manner, a phenomenon in whichwrinkles occur in the region near the reel-connected end portion mayoccur. The wrinkles may cause, for example, winding deviation, trackdeviation, or the like, during running. The phenomenon in which thewrinkles occur may not occur in a case where the wound state lasts for ashort time, but is prone to occur in a case where the above state lastsfor a long time. For example, the magnetic recording medium may be woundaround the reel in the magnetic recording and reproducing apparatus butthis state in which the magnetic recording medium is wound around thereel in the apparatus generally lasts only for a short time so the abovephenomenon does not occur. Meanwhile, the state in which the magneticrecording medium is wound around the reel in the magnetic recordingcartridge lasts particularly for a long time in a case where thecartridge is stored for a long time. Therefore, the phenomenon may occurin the magnetic recording medium in the magnetic recording cartridge.

In the magnetic recording cartridge according to the embodiment of thepresent technology, a difference between the servo track widths of theinner and outer sides of winding is a positive value, that is, the servotrack width of the inner side of the winding is larger than the servotrack width of the outer side of the winding. Thus, the servo trackwidth of the region near the reel-connected end portion is larger thanthe servo track width of the region near the outer end portion.Therefore, in a case where the magnetic recording medium is wound aroundthe reel in the magnetic recording cartridge, a longitudinal tensionapplied to winding in the region near the reel-connected end portion isstronger and a longitudinal tension applied to winding in the regionnear the outer end portion is weaker to keep the servo track widthconstant. As a result, the magnetic recording medium is wound around thereel with the stronger tension in the region near the reel-connected endportion than in the region near the outer end portion. By winding themagnetic recording medium in this manner, it is possible to prevent theoccurrence of wrinkles in the region near the reel-connected endportion.

The difference in servo track width between the inner and outer sides ofwinding may be, for example, 2.5 μm or less, preferably 1.8 μm or less,and more preferably 1.5 μm or less, 1.0 μm or less, 0.8 μm or less, or0.5 μm or less. Since the difference between the servo track widths ofthe inner and outer sides of winding is equal to or less than the upperlimit value, the width of the magnetic recording medium may be moreeasily kept constant by tension adjustment.

According to a preferred embodiment of the present technology, themagnetic recording medium may have a servo track width larger than aservo read head width of the magnetic recording and reproducingapparatus in which the magnetic recording cartridge is loaded (in whichmagnetic recording to the magnetic recording medium and/or magneticreproducing from the magnetic recording medium is performed). Morepreferably, the magnetic recording medium may have a servo track widthlarger than a servo read head width over the entire length of an innerregion sandwiched to positions 50 m away from both the end portions ofthe magnetic recording medium. Since the magnetic recording medium has aservo track width larger than the servo read head width, it is possibleto prevent the occurrence of winding deviation when the magneticrecording medium is wound around the reel in the magnetic recording andreproducing apparatus. The method of measuring the difference in servotrack width may be the same as the method of measuring the difference inservo track width described above regarding the difference in the servotrack width between the inner and outer sides of winding, and this willbe described in (3) of 2. below.

In a case where the magnetic recording medium has a servo track widthsmaller than the servo read head width, the longitudinal tension of themagnetic recording medium is loosened by the magnetic recording andreproducing apparatus for adjusting the longitudinal tension of themagnetic recording medium described above, and the tape width isexpanded. However, the loosening of the tension may cause windingdeviation.

In the present embodiment, since the magnetic recording medium has aservo track width larger than the servo read head width, thelongitudinal tension may be increased by the magnetic recording andreproducing apparatus. Accordingly, the occurrence of winding deviationmay be prevented.

Furthermore, the present technology provides a magnetic recordingcartridge including a magnetic recording medium in which an averagethickness t_(T) is t_(T)≤5.6 μm, a dimensional change amount Δw in awidth direction with respect to a change in tension in a longitudinaldirection is 660 ppm/N≤Δw, and a squareness ratio in a verticaldirection is 65% or more, in which the magnetic recording medium has aservo track width larger than a servo read head width of a magneticrecording and reproducing apparatus in which the magnetic recordingcartridge is loaded. The magnetic recording cartridge has a highrecording capacity and is suitable for use in a recording andreproducing apparatus that adjusts tension in the longitudinaldirection. The magnetic recording cartridge may prevent windingdeviation that may occur with the tension adjustment. Also, for thismagnetic recording cartridge, any one or a combination of two or more ofthe configurations described for the magnetic recording cartridge in thepresent specification may be introduced.

The magnetic recording medium included in the magnetic recordingcartridge according to the embodiment of the present technology ispreferably a long-shaped magnetic recording medium, and may be, forexample, a magnetic recording tape (in particular, a long-shapedmagnetic recording tape).

The magnetic recording medium included in the magnetic recordingcartridge according to the embodiment of the present technology may havea magnetic layer, a base layer, and a back layer, and may include anyother layer in addition to those layers. The other layer may beappropriately selected according to types of magnetic recording medium.The magnetic recording medium may be, for example, a coating typemagnetic recording medium or a vacuum thin film type magnetic recordingmedium. The coating type magnetic recording medium will be described inmore detail in 2. below. The vacuum thin film type magnetic recordingmedium will be described in more detail in 3. below. For the layersincluded in the magnetic recording medium other than the above threelayers, those descriptions may be referred to.

The magnetic recording medium included in the magnetic recordingcartridge according to the embodiment of the present technology mayhave, for example, at least one data band and at least two servo bands.The number of the data bands may be, for example, 2 to 10, particularly,3 to 6, and more particularly, 4 or 5. The number of the servo bands maybe, for example, 3 to 11, particularly, 4 to 7, and more particularly, 5or 6. These servo bands and data bands may be arranged, for example, toextend in the longitudinal direction of the long-shaped magneticrecording medium (in particular, a magnetic recording tape), and inparticular, to be substantially parallel. The data bands and the servobands may be provided in the magnetic layer. The magnetic recordingmedia having the data bands and the servo bands may include a magneticrecording tape conforming to the linear tape-open (LTO) standard. Inother words, the magnetic recording medium may be a magnetic recordingtape conforming to the LTO standard. For example, the magnetic recordingmedium may be a magnetic recording tape conforming to LTO8 or a laterstandard (e.g., LTO9, LTO10, LTO11, LTO12, etc.).

A width of the long-shaped magnetic recording medium (particularly,magnetic recording tape) may be, for example, 5 mm to 30 mm,particularly, 7 mm to 25 mm, more particularly, 10 mm to 20 mm, and evenmore particularly, 11 mm to 19 mm. The length of the long-shapedmagnetic recording medium (in particular, the magnetic recording tape)may be, for example, 500 m to 1,500 m. For example, a tape widthaccording to the LTO8 standard is 12.65 mm and a length is 960 m.

2. FIRST EMBODIMENT (EXAMPLE OF MAGNETIC RECORDING CARTRIDGE INCLUDINGCOATING TYPE MAGNETIC RECORDING MEDIUM) (1) Configuration of MagneticRecording Cartridge

First, a configuration of a magnetic recording cartridge according tothe embodiment of the present technology will be described withreference to FIG. 1A. FIG. 1A is a schematic view of an example of amagnetic recording cartridge according to the embodiment of the presenttechnology. The magnetic recording cartridge 1 shown in FIG. 1A includesa reel 3 provided in a cartridge case 2. A magnetic recording medium 10(in particular, a magnetic recording tape) is wound around the reel 3.

Next, a configuration of the magnetic recording medium 10 will bedescribed with reference to FIG. 1B. The magnetic recording medium 10is, for example, a magnetic recording medium subjected to verticalalignment processing, and as shown in FIG. 1B, and includes along-shaped base layer (also referred to as substrate) 11, a groundlayer (non-magnetic layer) 12 provided on one principal plane of thebase layer 11, a magnetic layer (or record layer) 13 provided on theground layer 12, and a back layer 14 provided on the other principalplane of the base layer 11. Hereinafter, among the both principal planesof the magnetic recording medium 10, the plane on which the magneticlayer 13 is provided will be referred to as a magnetic surface, and theplane opposite to the magnetic surface (the plane on which the backlayer 14 is provided) will be referred to as a back surface.

The magnetic recording medium 10 has a long shape and runs in thelongitudinal direction during recording and reproducing. Furthermore,the magnetic recording medium 10 may be configured to be able to recorda signal at a shortest recording wavelength of preferably 100 nm orless, more preferably 75 nm or less, still more preferably 60 nm orless, particularly preferably 50 nm or less, and may be used for, forexample, a recording and reproducing apparatus whose shortest recordingwavelength is in the above range. The recording and reproducingapparatus may include a ring type head as a recording head. A recordingtrack width is, for example, 2 μm or less.

(2) Description of Each Layer

(Base Layer)

The base layer 11 may function as a support of the magnetic recordingmedium 10, and may be, for example, a long shaped flexible non-magneticsubstrate, and in particular, may be a non-magnetic film. A thickness ofthe base layer 11 may be, for example, 2 μm to 8 μm, preferably 2.2 μmto 7 μm, more preferably 2.5 μm to 6 μm, and still more preferably 2.6μm to 5 μm. The base layer 11 may contain, for example, at least one ofa polyester-based resin, a polyolefin-based resin, a cellulosederivative, a vinyl-based resin, an aromatic polyether ketone resin, orany other polymer resin. In a case where the base layer 11 contains twoor more of the above-described materials, the two or more materials maybe mixed, copolymerized, or stacked.

Examples of the polyester-based resin may include one or a mixture oftwo or more of polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polybutylene terephthalate (PBT), polybutylenenaphthalate (PBN), polycyclohexylene dimethylene terephthalate (PCT),polyethylene-p-oxybenzoate (PEB), and polyethylenebisphenoxycarboxylate.According to a preferred embodiment of the present technology, the baselayer 11 may include PET or PEN.

The polyolefin-based resin may be, for example, one or a mixture of twoor more of polyethylene (PE) and polypropylene (PP).

The cellulose derivative may be, for example, one or a mixture of two ormore of cellulose diacetate, cellulose triacetate, cellulose acetatebutyrate (CAB), and cellulose acetate propionate (CAP).

The vinyl-based resin may be, for example, one or a mixture of two ormore of polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC).

The aromatic polyether ketone resin may be, for example, one or amixture of two or more of polyether ketone (PEK), polyether ether ketone(PEEK), polyether ketone ketone (PEKK), and polyether ether ketoneketone (PEEKK). According to a preferred embodiment of the presenttechnology, the base layer 11 may include PEEK.

Examples of any other polymer resin may be, for example, one or amixture of two or more of polyamide (PA, nylon), aromatic PA (aromaticpolyamide, aramid), polyimide (PI), aromatic PI, polyamide imide (PAI),aromatic PAI, polybenzoxazole (PBO) (e.g., Zylon (registeredtrademark)), polyether, polyether ester, polyether sulfone (PES),polyether imide (PEI), polysulfone (PSF), polyphenylene sulfide (PPS),polycarbonate (PC), polyarylate (PAR), and polyurethane (PU).

(Magnetic Layer)

The magnetic layer 13 may be, for example, a perpendicular record layer.The magnetic layer 13 may contain magnetic powder. The magnetic layer 13may further contain, for example, a binder and conductive particles inaddition to the magnetic powder. The magnetic layer 13 may furthercontain, for example, additives such as a lubricant, an abrasive, acorrosion inhibitor, and the like, as necessary.

An average thickness tm of the magnetic layer 13 is preferably 35nm≤tm≤120 nm, more preferably 35 nm≤tm≤100 nm, and particularlypreferably 35 nm≤tm≤90 nm. When the average thickness tm of the magneticlayer 13 is within the above numerical range, the magnetic layer 13contributes to improvement of electromagnetic conversion characteristic.

The average thickness tm of the magnetic layer 13 may be obtained asfollows. First, a specimen is fabricated by processing the magneticrecording medium 10 perpendicularly to a main surface thereof, and across-section of the specimen is observed by a transmission electronmicroscope (TEM) under the following conditions.

Device: TEM (H9000NAR manufactured by Hitachi, Ltd.)

Acceleration voltage: 300 kV

Magnification: 100,000 times

Next, using an obtained TEM image, a thickness of the magnetic layer 13is measured at positions of at least 10 spots in the longitudinaldirection of the magnetic recording medium 10, and thereafter, themeasured values are simply averaged (arithmetic mean) to be determinedas an average thickness tm (nm) of the magnetic layer 13.

The magnetic layer 13 is preferably a vertically aligned magnetic layer.In the present specification, vertical alignment refers to that asquareness ratio S1 measured in the longitudinal direction (runningdirection) of the magnetic recording medium 10 is 35% or less. A methodof measuring the squareness ratio S1 will be described separately below.

Note that the magnetic layer 13 may be a magnetic layer which isin-plane aligned (longitudinal alignment). In other words, the magneticrecording medium 10 may be a horizontal recording type magneticrecording medium. However, vertical alignment is more preferable interms of higher recording density.

(Magnetic Powder)

Examples of magnetic particles forming magnetic powder contained in themagnetic layer 13 may contain epsilon type iron oxide (ε iron oxide),gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide,hexagonal ferrite, barium ferrite (BaFe), Co ferrite, strontium ferrite,a metal, or the like, but are not limited thereto. The magnetic powdermay be one or a combination or two or more thereof. In particular,preferably, the magnetic powder may contain ε iron oxide magneticpowder, barium ferrite magnetic powder, cobalt ferrite magnetic powder,or strontium ferrite magnetic powder. Note that ε iron oxide may containGa and/or Al. These magnetic particles may be appropriately selected bythose skilled in the art on the basis of factors such as, for example,the method of manufacturing the magnetic layer 13, specifications of thetape, a function of the tape, and the like.

An average particle size (average maximum particle size) D of themagnetic powder may be preferably 22 nm or less, more preferably 8 nm to22 nm, and still more preferably 10 nm to 20 nm.

The average particle size D of the above magnetic powder is obtained asfollows. First, the magnetic recording medium 10 to be measured isprocessed by a focused ion beam (FIB) method or the like to produce athin piece, and a cross-section of the thin piece is observed by atransmission electron microscope (TEM). Next, 500 ε iron oxide particlesare randomly selected from the captured TEM image, a maximum particlesize d_(max) of each particle is measured, and a particle sizedistribution of the maximum particle size d_(max) of the magnetic powderis obtained. Here, the “maximum particle size d_(max)” refers to theso-called maximum Feret diameter. Specifically, the “maximum particlesize d_(max)” refers to a maximum distance among distances between twoparallel lines drawn from all angles so as to be in contact with outlineof the ε iron oxide particle. Thereafter, a median diameter (50%diameter, D50) of the maximum particle size d_(max) is obtained from theparticle size distribution of the obtained maximum particle sized_(max), and is determined as an average particle size (average maximumparticle size) D of the magnetic powder.

A shape of the magnetic particles depends on a crystal structure of themagnetic particles. For example, BaFe and strontium ferrites may have ahexagonal plate shape. The ε iron oxide may be spherical. The cobaltferrite may be cubic. The metal may have a spindle shape. These magneticparticles are aligned in a manufacturing process of the magneticrecording medium 10.

According to a preferred embodiment of the present technology, themagnetic powder may contain powder of nanoparticles preferablycontaining ε iron oxide (hereinafter, referred to as “ε iron oxideparticles”). Even with the fine particles of ε iron oxide particles,high coercive force can be obtained. Preferably, the ε iron oxidecontained in the ε iron oxide particle is preferentially crystal-alignedin a thickness direction (vertical direction) of the magnetic recordingmedium 10.

The ε iron oxide particles have a spherical or substantially sphericalshape or have a cubic or substantially cubic shape. Since the ε ironoxide particles have the shape as mentioned above, in a case where εiron oxide particles are used as the magnetic particles, a contact areabetween particles in a thickness direction of the medium is reduced tothus suppress aggregation of the particles, as compared with a casewhere barium ferrite particles having a hexagonal plate-like shape areused as magnetic particles. Therefore, dispersibility of the magneticpowder may be increased to thus obtain a better signal-to-noise ratio(SNR).

The ε iron oxide particles have a core-shell type structure.Specifically, as shown in FIG. 2, the ε iron oxide particle includes acore portion 21 and a shell portion 22 provided around the core portion21 and having a two-layer structure. The shell portion 22 having thetwo-layer structure includes a first shell portion 22 a provided on thecore portion 21 and a second shell portion 22 b provided on the firstshell portion 22 a.

The core portion 21 contains ε iron oxide. The ε iron oxide contained inthe core portion 21 preferably has an ε-Fe₂O₃ crystal as a main phase,and more preferably includes a single phase ε-Fe₂O₃.

The first shell portion 22 a covers at least a portion of the peripheryof the core portion 21. Specifically, the first shell portion 22 a maypartially cover the periphery of the core portion 21 or may cover theentire periphery of the core portion 21. If exchange coupling of thecore portion 21 and the first shell portion 22 a is sufficient and interms of improvement of magnetic characteristic, the first shell portion22 a preferably covers the entire surface of the core portion 21.

The first shell portion 22 a is a so-called soft magnetic layer, and maycontain, for example, a soft magnetic material such as α-Fe, a Ni—Fealloy, an Fe—Si—Al alloy, or the like. α-Fe may be obtained by reducingthe ε iron oxide contained in the core portion 21.

The second shell portion 22 b is an oxide film as an anti-oxidationlayer. The second shell portion 22 b may contain α iron oxide, aluminumoxide, or silicon oxide. The α iron oxide may contain, for example, atleast one of Fe₃O₄, Fe₂O₃, or FeO. In a case where the first shellportion 22 a contains α-Fe (soft magnetic material), the α-iron oxidemay be obtained by oxidizing α-Fe contained in the first shell portion22 a.

Since the ε iron oxide particles have the first shell portion 22 a asdescribed above, thermal stability may be ensured, whereby the coerciveforce Hc of the single core portion 21 may be maintained at a largevalue and/or the overall coercive force Hc of the ε iron oxide particles(core shell type particles) may be adjusted to the coercive force Hcappropriate for recording. Furthermore, since the ε iron oxide particleshave the second shell portion 22 b as described above, the ε iron oxideparticles are prevented from being exposed in the air during or beforethe manufacturing process of the magnetic recording medium 10 to causethe particle surfaces to be rusted, or the like, and thus, a degradationof the characteristic of the ε iron oxide particles can be suppressed.Therefore, a degradation of the characteristics of the magneticrecording medium 10 may be suppressed.

The ε iron oxide particle may have a shell portion 23 having a singlelayer structure as shown in FIG. 6. In this case, the shell portion 23has a configuration similar to that of the first shell portion 22 a.However, from the viewpoint of suppressing the degradation of thecharacteristics of the ε iron oxide particle, the ε iron oxide particlepreferably has the shell portion 22 having a two-layer structure.

The ε iron oxide particle may contain an additive instead of thecore-shell type structure, or may have the core-shell type structure andmay contain the additive as well. In these cases, a part of Fe of the εiron oxide particle is replaced by the additive. Since the coerciveforce Hc of the entire ε iron oxide particle may be adjusted to thecoercive force Hc suitable for recording also by the ε iron oxideparticle containing the additive, ease of recording may be improved. Theadditive is one or more selected from the group including metal elementother than iron, preferably trivalent metal element, more preferablyaluminum (Al), gallium (Ga), and indium (In).

Specifically, the ε iron oxide containing the additive is an ε-Fe₂-xMxO₃crystal (where, M is one or more selected from the group including metalelements other than iron, preferably trivalent metal elements, morepreferably Al, Ga, and In) and x is, for example, 0<x<1).

According to another preferred embodiment of the present technology, themagnetic powder may be barium ferrite (BaFe) magnetic powder. The bariumferrite magnetic powder contains magnetic particles of iron oxidecontaining barium ferrite as a main phase (hereinafter referred to as“barium ferrite particles”). The barium ferrite magnetic powder has highreliability of data recording, for example, in that the coercive forceis not lowered even in a high temperature and high humidity environment,and the like. From this viewpoint, barium ferrite magnetic powder ispreferable as the magnetic powder.

An average particle size of the barium ferrite magnetic powder is 50 nmor less, more preferably 10 nm to 40 nm, and still more preferably 12 nmto 25 nm.

In a case where the magnetic layer 13 contains the barium ferritemagnetic powder as magnetic powder, an average thickness tm [nm] of themagnetic layer 13 is preferably 35 nm≤t_(m)≤100 nm. Furthermore, thecoercive force Hc of the magnetic recording medium 10 measured in athickness direction (vertical direction) is preferably 160 kA/m to 280kA/m, more preferably 165 kA/m to 275 kA/m, and still more preferably170 kA/m to 270 kA/m.

According to yet another preferred embodiment of the present technology,the magnetic powder may be cobalt ferrite magnetic powder. The cobaltferrite magnetic powder contains magnetic particles of iron oxidecontaining cobalt ferrite as a main phase (hereinafter referred to as“cobalt ferrite magnetic particles”). The cobalt ferrite magneticparticles preferably have uniaxial anisotropy. The cobalt ferritemagnetic particles have, for example, a cubic shape or a substantiallycubic shape. The cobalt ferrite is cobalt ferrite containing Co. Thecobalt ferrite may further contain one or more selected from the groupincluding Ni, Mn, Al, Cu, and Zn in addition to Co.

The cobalt ferrite has, for example, an average composition representedby the following Formula (1).Co_(x)M_(y)Fe₂O_(z)  (1)

(where, in Formula (1), M is, for example, one or more metals selectedfrom the group including Ni, Mn, Al, Cu, and Zn; x is a value within arange of 0.4≤x≤1.0; y is a value within the range of 0≤y≤0.3; however, xand y satisfy the relationship of (x+y)≤1.0; z is a value within a rangeof 3≤z≤4; a part of Fe may be substituted by another metal element).

An average particle size of the cobalt ferrite magnetic powder ispreferably 25 nm or less, more preferably 23 nm or less. The coerciveforce Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe ormore, and more preferably 2600 Oe or more and 3500 Oe or less.

According to yet another preferred embodiment of the present technology,the magnetic powder may contain powder of nanoparticles containinghexagonal ferrite (hereinafter, referred to as “hexagonal ferriteparticles”). The hexagonal ferrite particle has, for example, ahexagonal plate shape or a substantially hexagonal plate shape. Thehexagonal ferrite may preferably contain at least one of Ba, Sr, Pb orCa, and more preferably at least one of Ba or Sr. The hexagonal ferritemay be, for example, barium ferrite or strontium ferrite. The bariumferrite may further contain at least one of Sr, Pb, or Ca in addition toBa. The strontium ferrite may further contain at least one of Ba, Pb orCa in addition to Sr.

More specifically, the hexagonal ferrite may have an average compositionrepresented by a general formula MFe₁₂O₁₉. Here, M is, for example, atleast one metal of Ba, Sr, Pb, and Ca, preferably at least one metal ofBa and Sr. M may be a combination of Ba and at least one metal selectedfrom the group including Sr, Pb, and Ca. Furthermore, M may be acombination of Sr and one or more metals selected from the groupincluding Ba, Pb, and Ca. In the above general formula, part of Fe maybe substituted by another metal element.

In a case where the magnetic powder contains powder of hexagonal ferriteparticles, an average particle size of the magnetic powder is preferably50 nm or less, more preferably 10 nm to 40 nm, and still more preferably15 nm to 30 nm.

(Binder)

The binder is preferably a resin having a structure in which acrosslinking reaction is given to a polyurethane-based resin, a vinylchloride-based resin, or the like. However, the binder is not limitedthereto, and any other resins may be appropriately mixed depending onphysical properties and the like desired for the magnetic recordingmedium 10. The resin to be mixed is not particularly limited as long asit is a resin generally used in the coating type magnetic recordingmedium 10.

The binder may include, for example, polyvinyl chloride, polyvinylacetate, a vinyl chloride-vinyl acetate copolymer, a vinylchloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrilecopolymer, an acrylic acid ester-acrylonitrile copolymer, an acrylicacid ester-vinyl chloride-vinylidene chloride copolymer, an acrylic acidester-acrylonitrile copolymer, an acrylic acid ester-vinylidene chloridecopolymer, a methacrylic acid ester-vinylidene chloride copolymer amethacrylic acid ester-vinyl chloride copolymer, a methacrylic acidester-ethylene copolymer, a polyvinyl fluoride, vinylidenechloride-acrylonitrile copolymer, an acrylonitrile-butadiene copolymer,a polyamide resin, polyvinyl butyral, a cellulose derivative (celluloseacetate butyrate, cellulose diacetate, cellulose triacetate, cellulosepropionate, and nitrocellulose), a styrene-butadiene copolymer, apolyester resin, an amino resin, synthetic rubber, and the like.

Furthermore, as the binder, a thermosetting resin or a reactive resinmay be used, and examples thereof include a phenol resin, an epoxyresin, a urea resin, a melamine resin, an alkyd resin, a silicone resin,a polyamine resin, an urea-formaldehyde resin, and the like.

Furthermore, polar functional groups such as, —SO₃M, —OSO₃M, —COOM,P═O(OM)₂, or the like, may be introduced into each binder describedabove in order to improve dispersibility of the magnetic powder. Here,in the formula, M is a hydrogen atom or an alkali metal such as lithium,potassium, sodium, and the like.

Moreover, examples of the polar functional group may include a sidechain type having an end group of —NR1R2 and —NR1R2R3⁺X— or a main chaintype of >NR1R2⁺X⁻. Here, in the formulas, R1, R2 and R3 are a hydrogenatom or a hydrocarbon group, and X— is a halogen element ion such asfluorine, chlorine, bromine, iodine, or the like, or an inorganic ororganic ion. Furthermore, the polar functional group may also include—OH, —SH, —CN, and an epoxy group.

(Additive)

The magnetic layer 13 may further contain aluminum oxide (α, β or γalumina), chromium oxide, silicon oxide, diamond, garnet, emery, boronnitride, titanium carbide, silicon carbide, titanium carbide, titaniumoxide (rutile type titanium carbide or anatase type titanium oxide), orthe like, as nonmagnetic reinforcing particles.

(Ground Layer)

The ground layer 12 is a nonmagnetic layer containing nonmagnetic powderand a binder as main components. The above description regarding thebinder contained in the magnetic layer 13 is also applied to the bindercontained in the ground layer 12. The ground layer 12 may furthercontain at least one of additives among conductive particles, alubricant, a curing agent, a rust-preventive agent, or the like, asnecessary.

An average thickness of the ground layer 12 is preferably 0.6 μm to 2.0μm, and more preferably 0.8 μm to 1.4 μm. Note that the averagethickness of the ground layer 12 is obtained in a manner similar to thatof the average thickness t_(m) of the magnetic layer 13. However, amagnification of a TEM image is appropriately adjusted according to thethickness of the ground layer 12.

(Nonmagnetic Powder)

The nonmagnetic powder contained in the ground layer 12 may include, forexample, at least one selected from inorganic particles and organicparticles. One kind of nonmagnetic powder may be used alone, or two ormore kinds of nonmagnetic powder may be used in combination. Theinorganic particles include, for example, one or a combination of two ormore selected from metal, metal oxide, metal carbonate, metal sulfate,metal nitride, metal carbide, and metal sulfide. More specifically, theinorganic particles may be, for example, one or two or more selectedfrom iron oxyhydroxide, hematite, titanium oxide, and carbon black. Ashape of the nonmagnetic powder may include, for example, various shapessuch as a needle shape, sphere shape, cubic shape, plate shape, or thelike, but is not particularly limited thereto.

(Back Layer)

The back layer 14 may contain a binder and nonmagnetic powder. The backlayer 14 may contain various additives such as a lubricant, a curingagent, an antistatic agent, and the like, as necessary. The abovedescription of the binder and the nonmagnetic powder contained in theground layer 12 is also applied to the binder and the nonmagnetic powdercontained in the back layer 14.

An average particle size of the inorganic particles contained in theback layer 14 is preferably 10 nm to 150 nm, and more preferably 15 nmto 110 nm. The average particle size of the inorganic particles isobtained in a manner similar to that of the average particle size D ofthe magnetic powder described above.

An average thickness t_(b) of the back layer 14 is preferably t_(b)≤0.6μm. Since the average thickness t_(b) of the back layer 14 is within theabove range, even in a case where the average thickness t_(T) of themagnetic recording medium 10 is t_(T)≤5.5 μm, the thicknesses of theground layer 12 and the base layer 11 may be kept thick, whereby runningstability of the magnetic recording medium 10 in the recording andreproducing apparatus may be maintained.

The average thickness t_(b) of the back layer 14 is obtained as follows.First, a ½ inch-wide magnetic recording medium 10 is prepared and cutinto a length of 250 mm to prepare a sample. Next, thicknesses ofdifferent spots of the sample are measured at 5 or more points using alaser hologage manufactured by Mitsutoyo Co., Ltd., as a measurementdevice, and the measured values are simply averaged (arithmetic average)to obtain an average value t_(T) [μm]. Subsequently, the back layer 14of the sample is removed with a solvent such as methyl ethyl ketone(MEK) or diluted hydrochloric acid, and thereafter, thicknesses ofdifferent spots of the sample are measured at 5 or more points using thelaser hologage and the measured values are simply averaged (arithmeticaverage) to obtain an average value t_(B) [μm]. Thereafter, the averagethickness t_(b) [μm] of the back layer 14 is obtained by the followingequation.t _(b) [μm]=t _(T) [μm]−t _(B) [μm]

(3) Physical Properties and Structure

(Average Thickness t_(T) of Magnetic Recording Medium)

The average thickness t_(T) of the magnetic recording medium 10 ist_(T)≤5.6 μm. When the average thickness t_(T) of the magnetic recordingmedium 10 is t_(T)≤5.6 μm, a recording capacity that can be recorded inone data cartridge can be increased as compared to the related art. Alower limit value of the average thickness t_(T) of the magneticrecording medium 10 is, for example, 3.5 μm≤t_(T), but is notparticularly limited.

The average thickness t_(T) of the magnetic recording medium 10 isobtained by the method of measuring the average value t_(T) describedabove in the method of measuring the average thickness t_(b) of the backlayer 14.

(Dimensional Change Amount Δw)

The dimensional change amount Δw [ppm/N] of the magnetic recordingmedium 10 in the width direction with respect to a change in tension ofthe magnetic recording medium 10 in the longitudinal direction is 660ppm/N≤Δw, more preferably 670 ppm/N≤Δw, more preferably 700 ppm/N≤Δw,more preferably 710 ppm/N≤Δw, more preferably 730 ppm/N≤Δw, morepreferably 750 ppm/N≤Δw, still more preferably 780 ppm/N≤Δw, andparticularly preferably 800 ppm/N≤Δw. If the dimensional change amountΔw is Δw≤640 ppm/N, it may be difficult to suppress a change in width inthe adjustment of longitudinal tension by the recording and reproducingapparatus. The upper limit value of the dimensional change amount Δw isnot particularly limited. For example, Δw≤1700000 ppm/N, preferablyΔw≤20000 ppm/N, more preferably Δw≤8000 ppm/N, still more preferablyΔw≤5000 ppm/N, Δw≤4000 ppm/N, Δw≤3000 ppm/N, or Δw≤2000 ppm/N.

Those skilled in the art can appropriately set the dimensional changeamount Δw. For example, the dimensional change amount Δw may be set to adesired value by selecting a thickness of the base layer 11 and/or amaterial of the base layer 11. Furthermore, the dimensional changeamount Δw may be set to a desired value, for example, by adjusting thestretching strength in the vertical and horizontal directions of thefilm constituting the base layer. For example, Δw decreases more whenthe film is stretched more strongly in the width direction, andconversely, Δw increases when the film is stretched strongly in thelongitudinal direction.

The dimensional change amount Δw is obtained as follows. First, a ½inch-wide magnetic recording medium 10 is prepared and cut into a lengthof 250 mm to prepare a sample 10S. Next, loads are applied in order of0.2 N, 0.6 N, and 1.0 N in the longitudinal direction of the sample 10S,and widths of the sample 10S at the loads of 0.2 N, 0.6 N, and 1.0 N aremeasured. Subsequently, the dimensional change amount Δw is determinedfrom the following equation. Note that the measurement in a case ofapplying the load of 0.6 N is carried out to check whether anabnormality has not occurred in the measurement (in particular, in orderto check whether these three measurement results are linear), and themeasurement results are not used in the following equation.

$\begin{matrix}{{\Delta\;{w\left\lbrack {{ppm}/N} \right\rbrack}} = {\frac{{{D\left( {0.2\mspace{11mu} N} \right)}\lbrack{mm}\rbrack} - {{D\left( {1.0\mspace{11mu} N} \right)}\lbrack{mm}\rbrack}}{{D\left( {0.2\mspace{11mu} N} \right)}\lbrack{mm}\rbrack} \times \frac{1,000,000}{\left( {1.0\lbrack N\rbrack} \right) - \left( {0.2\lbrack N\rbrack} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

(where, D(0.2 N) and D(1.0 N) represent widths of the sample 10S when0.2 N and 1.0 N are loaded in the longitudinal direction of sample 10S,respectively).

The widths of the sample 10S when each load is applied are measured asfollows. First, a measurement device shown in FIG. 3A including adigital dimension measuring instrument LS-7000 manufactured by KeyenceCorporation is prepared as a measurement device, and the sample 10S isset in the measurement device. Specifically, one end of the long-shapedsample (magnetic recording medium) 10S is fixed by a fixing portion 231.Next, as shown in FIG. 3A, the sample 10S is placed on fivesubstantially cylindrical and rod-like support members 232. The sample10S is placed on the five support members 232 so that a back surfacethereof is in contact with the five support members 232. The fivesupport members 232 (particularly, surfaces thereof) all includestainless steel SUS304, and surface roughness Rz (maximum height)thereof is 0.15 μm to 0.3 μm.

The arrangement of the five rod-like support members 232 will bedescribed with reference to FIG. 3B. As shown in FIG. 3B, the sample 10Sis placed on the five support members 232. Hereinafter, the five supportmembers 232 will be referred to as, starting from the side closest tothe fixing portion 231, a “first support member”, a “second supportmember”, a “third support member” (having a slit 232A), a “fourthsupport member”, and a “fifth support member” (closest to a weight 233).A diameter of these five support members is 7 mm. A distance d₁ betweenthe first support member and the second support member (in particular, adistance between the centers of these support members) is 20 mm. Adistance d2 between the second support member and the third supportmember is 30 mm. A distance d3 between the third support member and thefourth support member is 30 mm. A distance d4 between the fourth supportmember and the fifth support member is 20 mm. Furthermore, the secondsupport member, the third support member, and the fourth support memberare arranged so that portions of the sample 10S placed between thesecond support member, the third support member, and the fourth supportmember forms a substantially perpendicular plane with respect to thedirection of gravity. Furthermore, the first support member and thesecond support member are arranged so that the sample 10S forms an angleof θ₁=30° with respect to the substantially perpendicular plane betweenthe first support member and the second support member. Moreover, thefourth support member and the fifth support member are arranged so thatthe sample 10S forms an angle of θ₂=30° with respect to thesubstantially perpendicular plane between the fourth support member andthe fifth support member.

Furthermore, among the five support members 232, the third supportmember is fixed so as not to rotate, while the other four supportmembers are all rotatable.

The sample 10S is held on the support member 232 so as not to move in awidth direction of the sample 10S. Note that, among the support members232, the support member 232 positioned between a light emitter 234 and alight receiver 235 and positioned substantially at the center betweenthe fixing portion 231 and a load applying portion has the slit 232A.Light L is irradiated from the light emitter 234 to the light receiver235 through the slit 232A. A slit width of the slit 232A is 1 mm and thelight L may pass through the width, without being blocked by the rim ofthe slit 232A.

Subsequently, after the measurement device is accommodated in a chambercontrolled in a predetermined environment controlled at a constanttemperature of 25° C. and a relative humidity of 50%, the weight 233 forapplying a load of 0.2 N is attached to the other end of the sample 10Sand the sample 10S is left for 2 hours in the environment. After 2hours, a width of the sample 10S is measured. Next, the weight forapplying the load of 0.2 N is changed to a weight for applying a load of0.6 N, and the width of the sample 10S is measured 5 minutes after theswitch. Finally, the weight is changed to a weight for applying a loadof 1.0 N, and the width of the sample 10S is measured 5 minutes afterthe switch.

As described above, by adjusting the weight of the weight 233, the loadapplied in the longitudinal direction of the sample 10S may be changed.With each load applied, light L is irradiated from the light emitter 234toward the light receiver 235, and the width of the sample 10S to whichthe load is applied in the longitudinal direction is measured. Themeasurement of the width is performed in a state where the sample 10S isnot curled. The light emitter 234 and the light receiver 235 areprovided in the digital dimension measuring instrument LS-7000.

(Thermal Expansion Coefficient α)

The thermal expansion coefficient α[ppm/° C.] of the magnetic recordingmedium 10 may be preferably 5.5 ppm/° C.≤α≤9 ppm/° C., and morepreferably 5.9 ppm/° C.≤α≤8 ppm/° C. When the thermal expansioncoefficient α is within the above range, a change in the width of themagnetic recording medium 10 may be further suppressed by adjustingtension in the longitudinal direction of the magnetic recording medium10 by the recording and reproducing apparatus.

The temperature expansion coefficient α is obtained as follows. First,the sample 10S is prepared in a manner similar to that of the method ofmeasuring the dimensional change amount Δw, the sample 10S is set in ameasurement device similar to that of the method of measuring thedimensional change amount Δw, and thereafter, the measurement device isaccommodated in a chamber of a predetermined environment controlled at atemperature of 29° C. and relative humidity of 24%. Next, a load of 0.2N is applied in the longitudinal direction of the sample 10S, and thesample 10S was placed in the above environment for 2 hours. Thereafter,with the relative humidity of 24% maintained, widths of the sample 10Sat 45° C., 29° C., and 10° C. are measured, while changing thetemperatures in order of 45° C., 29° C., and 10° C., and the temperatureexpansion coefficient α is obtained from the following equation. Here,the widths of the sample 10S are measured at these temperatures 2 hoursafter each temperature is reached. Note that the measurement at thetemperature of 29° C. is carried out in order to check whether anabnormality has not occurred in the measurement (in particular, to checkwhether these three measurement results are linear) and the measurementresults are not used in the following equation.

$\begin{matrix}{{\alpha\left\lbrack {{ppm}/{{{^\circ}C}.}} \right\rbrack} = {\frac{{{D\left( {45{^\circ}\mspace{14mu} C} \right)}\lbrack{mm}\rbrack} - {{D\left( {10{^\circ}\mspace{14mu}{C.}} \right)}\lbrack{mm}\rbrack}}{{D\left( {10{^\circ}\mspace{14mu}{C.}} \right)}\lbrack{mm}\rbrack} \times \frac{1,000,000}{\left( {45\left\lbrack {{^\circ}\mspace{14mu}{C.}} \right\rbrack} \right) - \left( {10\left\lbrack {{^\circ}\mspace{14mu}{C.}} \right\rbrack} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

(where, D(45° C.) and D(10° C.) represent the widths of the sample 10Sat the temperatures of 45° C. and 10° C., respectively).

(Humidity Expansion Coefficient β)

A humidity expansion coefficient β[ppm/% RH] of the magnetic recordingmedium 10 may be preferably β≤5.5 ppm/% RH, more preferably β≤5.2 ppm/%RH, and still more preferably β≤5.0 ppm/% RH. When the humidityexpansion coefficient β is within the range, a change in the width ofthe magnetic recording medium 10 can be further suppressed by adjustingtension in the longitudinal direction of the magnetic recording medium10 by the recording and reproducing apparatus.

The humidity expansion coefficient β is obtained as follows. First, thesample 10S is prepared in a manner similar to that of the method ofmeasuring the dimensional change amount Δw and set in a measurementdevice similar to that of the method of measuring the dimensional changeamount Δw, and thereafter, the measurement device is accommodated in achamber of a predetermined environment controlled at a temperature of29° C. and a relative humidity of 24%. Next, a load of 0.2 N is appliedin the longitudinal direction of the sample 10S, and the sample is leftin the environment for 2 hours. Thereafter, with the temperature of 29°C. maintained, widths of the sample 10S at relative humidity of 80%,24%, and 10% are measured, while the relative humidity is changed inorder of 80%, 24%, and 10%, and a humidity expansion coefficient β isobtained by the following equation. Here, the widths of the sample 10Sare measured at these pieces of humidity immediately after each humidityis reached. Note that the measurement at the humidity of 24% is carriedout in order to check whether an abnormality has not occurred in themeasurement, and the measurement results are not used in the followingequation.

$\begin{matrix}{{\beta\left\lbrack {{{ppm}/\%}\mspace{11mu}{RH}} \right\rbrack} = {\frac{{{D\left( {80\%} \right)}\lbrack{mm}\rbrack} - {{D\left( {10\%} \right)}\lbrack{mm}\rbrack}}{{D\left( {10\%} \right)}\lbrack{mm}\rbrack} \times \frac{1,000,000}{\left( {80\lbrack\%\rbrack} \right) - \left( {10\lbrack\%\rbrack} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

(where, D(80%) and D(10%) represent the widths of the sample 10S at therelative humidity 80% and 10%, respectively).

(Poisson's Ratio ρ)

A Poisson's ratio ρ of the magnetic recording medium 10 may bepreferably 0.25≤ρ, more preferably 0.29≤ρ, and still more preferably0.3≤ρ. When the Poisson's ratio ρ is within the above range, a change inthe width of the magnetic recording medium 10 can be further suppressedby adjusting tension in the longitudinal direction of the magneticrecording medium 10 by the recording and reproducing apparatus.

The Poisson's ratio ρ is obtained as follows. First, a ½ inch-widemagnetic recording medium 10 is prepared and cut into a length of 150 mmto prepare a sample, and a mark having a size of 6 mm×6 mm is given tothe center of the sample. Next, both end portions in the longitudinaldirection of the sample are chucked so that a distance between chucks is100 mm, an initial load of 2 N is applied, a length of the mark in thelongitudinal direction of the sample at that time is determined as aninitial length and a width of the mark in a width direction of thesample is determined as an initial width. Subsequently, the sample isstretched with an Instron type universal tensile tester at a tensilespeed of 0.5 mm/min and dimensional change amounts of the mark in thelength of the mark in the longitudinal direction of the sample and thewidth of the mark in the width direction of the sample are measured withan image sensor manufactured by Keyence Corporation. Thereafter,Poisson's ratio ρ is obtained from the following equation.

$\begin{matrix}{\rho = \frac{\left\{ \frac{\left( {{Dimensional}\mspace{14mu}{Change}\mspace{14mu}{Amount}\mspace{14mu}{of}\mspace{14mu}{Width}\mspace{14mu}{of}\mspace{14mu}{{Mark}\mspace{14mu}\lbrack{mm}\rbrack}} \right)}{\left( {{Initial}\mspace{14mu}{{Width}\mspace{14mu}\lbrack{mm}\rbrack}} \right)} \right\}}{\left\{ \frac{\left( {{Dimensional}\mspace{14mu}{Change}\mspace{14mu}{Amount}\mspace{14mu}{of}\mspace{14mu}{Length}\mspace{14mu}{of}\mspace{14mu}{{Mark}\mspace{14mu}\lbrack{mm}\rbrack}} \right)}{\left( {{Initital}\mspace{14mu}{{Width}\mspace{14mu}\lbrack{mm}\rbrack}} \right)} \right\}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

(Longitudinal Elasticity Limit Value σ_(MD))

The elasticity limit value σ_(MD)[N] in the longitudinal direction ofthe magnetic recording medium 10 may be preferably 0.7 N≤σ_(MD), morepreferably 0.75 N≤σ_(MD), and still more preferably 0.8 N≤σ_(MD). Whenthe elasticity limit value σ_(MD) is within the above range, a change inthe width of the magnetic recording medium 10 can be further suppressedby adjusting tension in the longitudinal direction of the magneticrecording medium 10 by the recording and reproducing apparatus.Furthermore, it is easier to control a drive side. An upper limit valueof the elasticity limit value σ_(MD) in the longitudinal direction ofthe magnetic recording medium 10 is not particularly limited and may be,for example, σ_(MD)≤5.0 N. Preferably, the elasticity limit value σ_(MD)does not depend on a speed V when an elastic limit is measured. Thereason is because, when the elastic limit value σ_(MD) does not dependon the speed V, the change in the width of the magnetic recording medium10 can be effectively suppressed without being affected by a runningspeed of the magnetic recording medium 10 in the recording andreproducing apparatus and a tension adjustment speed or responsivenessof the recording and reproducing apparatus. The elasticity limit valueσ_(MD) is set to a desired value, for example, depending on a selectionof curing conditions of the ground layer 12, the magnetic layer 13, andthe back layer 14, and or a selection of a material of the base layer11. For example, as a time for curing paint for forming the groundlayer, paint for forming the magnetic layer, and paint for forming theback layer is increased or as a curing temperature thereof is increased,a reaction between a binder and a curing agent contained in each paintis accelerated. As a result, elastic characteristic are improved toimprove the elasticity limit value GMD.

The elastic limit value GMD is obtained as follows. First, a ½ inch-widemagnetic recording medium 10 is prepared, cut into a length of 150 mm toprepare a sample, and both ends of the sample in the longitudinaldirection are chuck in the universal tensile tester so that a distanceλ0 between the chucks is 100 mm (λ0=100 mm). Next, the sample isstretched at a tensile speed of 0.5 mm/min, and a load σ(N) regardingthe distance λ(mm) between the chucks is continuously measured.Subsequently, a relationship between Δλ(%) and σ(N) is graphed using theobtained data of λ(mm) and σ(N). However, Δλ(%) is given by thefollowing equation.Δλ(%)=((λ−λ0)/λ0)×100

Next, in the above graph, a region in which the graph is a straight lineis calculated in the region of σ≥0.2 N and a maximum load σ thereof isset as an elasticity limit value σ_(MD)(N)

(Friction Coefficient μ Between Magnetic Surface and Back Surface)

A friction coefficient μ between the surface of the magnetic layer sideand the surface of the back layer side of the magnetic recording medium10 (hereinafter, also referred to as interlayer friction coefficient μ)is preferably 0.20≤μ≤0.80, more preferably 0.20≤μ≤0.78, and still morepreferably 0.25≤μ≤0.75. When the friction coefficient μ is within theabove range, handling properties of the magnetic recording medium 10 isimproved. For example, when the friction coefficient μ is within theabove range, the occurrence of winding deviation when the magneticrecording medium 10 is wound around the reel (for example, the reel 10C,etc., in FIG. 5) is suppressed. More specifically, in a case where thefriction coefficient μ is too small (for example, in case of μ<0.18), aninterlayer friction between a magnetic surface of a portion of themagnetic recording medium 10, which has already been wound around thecartridge reel, positioned on the outermost circumference and a backsurface of the magnetic recording medium 10 to be newly wound around anouter side thereof is extremely low and thus the magnetic recordingmedium 10 to be newly wound may readily deviate from the magneticsurface of the portion position on the outermost circumference of themagnetic recording medium 10 which has already been wound. Therefore,winding deviation of the magnetic recording medium 10 occurs. Meanwhile,in a case where the friction coefficient μ is too large (for example, incase of 0.82<μ or 0.80<μ), an interlayer friction between the backsurface of the magnetic recording medium 10 which is to be definitelyreleased from the outermost circumference of the reel on the drive sideand the magnetic surface of the magnetic recording medium 10, which ispositioned immediately thereunder and which is in a state of being woundyet on the reel on the drive side is extremely high, so the back surfaceand the magnetic surface are stuck to each other. Therefore, theoperation of the magnetic recording medium 10 toward the cartridge reelbecomes unstable, thereby causing winding deviation of the magneticrecording medium 10.

The friction coefficient μ is obtained as follows. First, the magneticrecording medium 10 having a width of ½ inches, with the back surfacefacing upward, is wound around a circumference having a diameter of 1inch so as to be fixed. Next, the magnetic recording medium 10 havingthe width of ½ inches is brought into contact with the circumference ata wrap angle of θ(°)=180°+1° to 180°−10° so that the magnetic surfacethereof is in contact therewith and one end of the magnetic recordingmedium 10 is connected to a movable strain gauge and tension T₀=0.6(N)is given to the other end of the magnetic recording medium 10. Thereading T₁(N) to T₈(N) of the movable strain gauge at each outward pathwhen the movable strain gauge is reciprocated 8 times at 0.5 mm/s ismeasured, and an average value of T₄ to T₈ is determined as T_(ave)(N).Thereafter, the friction coefficient μ is obtained from the followingequation.

$\begin{matrix}{\mu = {\frac{1}{\left( {\theta\lbrack{^\circ}\rbrack} \right) \times \left( {\pi/180} \right)} \times {\log_{e}\left( \frac{T_{ave}\;\lbrack N\rbrack}{T_{0\;}\lbrack N\rbrack} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

(Surface Roughness R_(ab) of Back Layer)

The surface roughness R_(ab) [nm] (in other words, surface roughness ofthe back surface) of the back layer 14 is preferably 7.5 nm or less,more preferably 7.2 nm or less, still more preferably 7.0 nm or less,6.5 nm or less, 6.3 nm or less, or 6.0 nm or less. Furthermore, thesurface roughness R_(ab) is preferably 3.0 nm or more, more preferably3.2 nm or more, and still more preferably 3.4 nm or more. When thesurface roughness R_(ab) of the back layer is within the above range,handling properties of the magnetic recording medium 10 can be improved.Furthermore, when the magnetic recording medium 10 is wound, aninfluence on the surface of the magnetic layer can be reduced, and thus,an adverse effect on the electromagnetic conversion characteristic canbe suppressed. The handling properties and electromagnetic conversioncharacteristic are contradictory properties, but the surface roughnessR_(ab) within the numerical range enables their compatibility.

The surface roughness R_(ab) of the back surface is obtained as follows.First, the magnetic recording medium 10 having a width of ½ inches isprepared, and the magnetic recording medium 10 is attached to a slideglass, with the back surface facing upward (that is, the magneticsurface is attached to the slide glass) to use it as a sample piece.Next, surface roughness of the back surface of the sample piece ismeasured by the following non-contact roughness meter using opticalinterference.

Device: Non-contact roughness meter using optical interference

(VertScan R5500GL-M100-AC, non-contact surface and layer cross-sectionalshape measurement system, manufactured by Ryoka Systems Inc.)

Objective lens: 20 times (approximately 237 μm×178 μm field of view)

Resolution: 640 points×480 points

Measurement mode: phase

Wavelength filter: 520 nm

Surface correction: correction by quadratic polynomial approximationplane

As described above, surface roughness is measured at positions of atleast five spots in the longitudinal direction, and an average value ofeach arithmetic average

roughness Sa (nm), which is automatically calculated from a surfaceprofile obtained at each position, is determined as the surfaceroughness R_(ab) (nm) of the back surface.

((Servo Track Width on Inner Side of Winding)−(Servo Track Width onOuter Side of Winding))

A difference between the servo track widths on the inner side of thewinding and the outer side of the winding exceeds 0 preferably 0.01 μmor more, more preferably 0.02 or more, and still more preferably 0.05 μmor more. The difference between servo track widths on the inner side ofthe winding and the outer side of the winding may be, for example, 0.10or more, 0.15 μm or more, or 0.20 μm or more. Accordingly, theoccurrence of wrinkles on the magnetic recording medium wound around thereel in the cartridge may be prevented.

The difference in servo track width between the inner and outer sides ofwinding may be, for example, 2.5 μm or less, preferably 1.8 μm or less,and more preferably 1.5 μm or less, 1.0 μm or less, 0.8 μm or less, or0.5 μm or less.

In order to obtain a difference between the servo track widths on theinner and outer sides of the winding, a

deviation amount T_(in)W of the servo track width on the inner side ofthe winding of the magnetic recording medium and a deviation amountT_(out)W of the servo track width on the outer side of the winding arerespectively measured. The measurement is carried out under anenvironment of a temperature of 23±3° C. and a relative humidity of50%±5%. These deviation amounts indicate how large or small the servotrack widths are, with respect to a standard servo track width. A methodof measuring these deviation amounts will be separately described below.

In this specification, on the basis of a position, as a starting point,50 m away from an end portion (hereinafter, referred to as an “inner endportion”) installed on the reel (around which the magnetic recordingmedium is wound) in the magnetic recording cartridge, the inner side ofthe winding refers to a region up to a position 10 m advancing from thestarting position in a direction toward an end portion (hereinafter,referred to as an “outer end portion”) opposite to the inner end portionof the two end portions of the magnetic recording medium.

In this specification, on the basis of a position, as a starting point,50 m away from the outer end portion, the outer side of the windingrefers to a region up to a position 10 m advancing from the startingposition in a direction toward the inner end portion of among the twoend portions of the magnetic recording medium.

The inner side and the outer side of the winding will be described inmore detail with reference to FIG. 11. In FIG. 11, an inner end portionE1 of the reel 3 of the magnetic recording cartridge 1 is provided. Aregion between a position A 50 m away from the inner end portion E1 anda position B 10 m away from the position A toward the outer end portionE2 is the inner side of the winding. A region between a position C 50 maway from the outer end portion E2 toward the inner end portion E1 and aposition D 10 m further away from the position C toward the inner endportion E1 is the outer side of the winding.

The deviation amount T_(in)W of the servo track width on the inner sideof the winding is measured, while allowing the magnetic recording mediumaccommodated in the magnetic recording cartridge to run so as to bedrawn into the magnetic recording and reproducing apparatus (that is,while allowing the magnetic recording medium to run in a forwarddirection). In the measurement, tension applied to the magneticrecording medium is 0.55 N and a running speed is 3 to 6 m/s. Theaverage value of the deviation amounts of the servo track widthsmeasured over the region of 10 m of the inner side of the winding isused as a deviation amount T_(in)W of the servo track width of the innerside of the winding to obtain the above difference. The average value iscalculated by a simple average.

The measurement of the deviation amount T_(out)W of the servo trackwidth on the outer side of the winding is also carried out, whileallowing the magnetic recording medium to run in the forward direction,similar to the inner side of the winding. The average value of thedeviation amounts of the servo track widths measured over the region of10 m of the outer side of the winding is used as a deviation amountT_(out)W of the servo track width of the outer side of the winding toobtain the above difference. The average value is also calculated by asimple average.

A difference (T_(in)W−T_(out)W) is obtained by subtracting the deviationamount T_(out)W of the servo track width on the outer side of thewinding from the deviation amount T_(in)W of the servo track width onthe inner side of the winding obtained as described above, and the abovedifference is (servo track width on inner side of winding)−(servo trackwidth on outer side of winding).

(Deviation Amount of Servo Track Width)

A method of measuring a deviation amount of the servo track width willbe described with reference to FIGS. 12A to 12C. FIG. 12A is a schematicdiagram of a data band and a servo band formed in a magnetic layer of amagnetic recording tape. As shown in FIG. 12A, the magnetic layer hasfour data bands d0 to d3. The magnetic layer has a total of five servobands S0 to S4 so that each data band is sandwiched by two servo bands.As shown in FIG. 12B, each servo band has repeated frame units eachincluding five servo signals S5 a inclined at a predetermined angle θ1,five servo signals S5 b inclined at the same angle in the oppositedirection of the servo signals S5 a, four servo signals S4 a inclined atthe predetermined angle θ1, and four servo signals S4 b inclined at thesame angle in the opposite direction of the servo signals S4 a. Theangle θ1 may be, for example, 5° to 25°, and particularly 11° to 20°.

The deviation amount of the servo track width measured in the abovemeasuring method is the deviation amount of the servo track widthbetween two servo tracks S1 and S2 sandwiching the second data band d1from the top in FIG. 12A with respect to a standard servo track width.

In a case where two servo tracks S1 and S2 sandwiching the data band d1are reproduced at the time of driving, a waveform as shown in FIG. 12Cis obtained for each servo track by a digital oscilloscope (WAVEPRO 960manufactured by Lecroy Corporation).

A time between the timing signals is obtained from the waveform obtainedby reproduction of the servo track S1 and a distance between a leadingmagnetic stripe of burst A and a leading magnetic stripe of burst B inthe servo track S1 is calculated from the time and a tape running speed.For example, as shown in FIG. 12B, a distance L1 between a leadingmagnetic stripe (the leftmost magnetic stripe among the five magneticstripes) of the burst A S5 a-1 and a leading magnetic stripe (theleftmost magnetic stripe among the five magnetic stripes) of the burst BS5 b-1 is calculated.

Similarly, a time between timing signals is obtained from a waveformobtained by reproduction of the servo track S2, and a distance betweenthe leading magnetic stripe of the burst A and the leading magneticstripe of the burst B in the servo track S2 is calculated from the timeand a tape running speed. For example, as shown in FIG. 11(b), adistance L2 between a leading magnetic stripe of the burst A S5 a-2 anda leading magnetic stripe of the burst B S5 b-2 is calculated.

For example, in a case where the magnetic recording tape is enlarged inthe width direction, for example, a time between timing signals obtainedby reproduction of the servo track S1 is lengthened, and as a result,the calculated distance L1 may also be increased. In a case where themagnetic recording tape is reduced in the width direction, thecalculated distance L1 may be reduced. Therefore, by using the distanceL1, the distance L2 and an azimuth angle, the deviation amount of theservo track width may be obtained. The deviation amount of the servotrack width is obtained from the following equation.(Deviation amount of servo track width)={(L1−L2)/2}×tan(90°−θ1)

In this equation, L1 and L2 are the distances L1 and L2 described above,and θ1 is the inclination angle θ1 described above and is also referredto as an azimuth angle. θ1 is obtained by developing the magneticrecording tape taken out from the cartridge with FERRICOLLOID developerand using a universal tool microscope (TOPCON TUM-220ES) and a dataprocessing device (TOPCON CA-1B).

The deviation amount of the servo track width is a change amount withrespect to a standard servo track width. The standard servo track widthmay be equal to the servo lead head width of the magnetic recording andreproducing apparatus and may be determined, for example, according tothe type of the magnetic recording medium 10 such as a standard that themagnetic recording medium 10 follows, and the like.

Note that the servo track width can be adjusted, for example, asfollows. In order to alleviate distortion occurring in the magneticrecording medium 10, winding tension may be lowered in a drying processof the magnetic recording medium 10 and/or a calendering process(heating region). Furthermore, in order to alleviate distortion in apancake state and/or a cartridge state after cutting, the magneticrecording medium 10 may be stored for a long time at a temperature of55° C. or higher. The servo track width may be adjusted by reducing thedistortion in this way.

(Servo Track Width Larger than Servo Lead Head Width)

The magnetic recording medium 10 preferably has a servo track widthlarger than the servo lead head width of the magnetic recording andreproducing apparatus in which the magnetic recording cartridge 1 isloaded. The servo track width is a servo track width between the servotracks S1 and S2 described above. The servo lead head width is a widthof two adjacent servo signal reading magnetic head gaps included in themagnetic recording and reproducing apparatus, and servo signals of twoadjacent servo bands are read by the two adjacent servo signal readingmagnetic head gaps, respectively. The servo lead head width may have,for example, the standard servo track width described above.

For example, the deviation amount T_(in)W of the servo track width onthe inner side of the winding and the deviation amount T_(out)W of theservo track width on the outer side of the winding are measured usingthe servo lead head width as the standard servo track width, and in acase where

both of the measured deviation amounts are positive values (for example,more than 0.00 μm), it is determined that the magnetic recording mediumhas a servo track width larger than the servo lead head width. In a casewhere one deviation amount is 0 or less or in a case where the deviationamount of both is 0 or less, it is determined that the magneticrecording medium does not have a servo track width larger than the servolead head width.

Preferably, both the deviation amount T_(in)W of the servo track widthon the inner side of the winding and the deviation amount T_(out)W ofthe servo track width on the outer side of the winding are preferably0.01 μm or more, more preferably 0.05 μm or more, and still morepreferably 0.10 μm or more.

The deviation amount T_(in)W of the servo track width on the inner sideof the winding and the deviation amount T_(out)W of the servo trackwidth on the outer side of the winding are both, for example, 5.0 μm orless, more preferably 4.0 μm or less, and still more preferably 3.0 μmor less, or 2.0 μm or less, or 1.0 μm or less.

The measurement of these deviation amounts is performed as describedabove.

(Coercive Force Hc)

The coercive force Hc measured in the thickness direction (verticaldirection) of the magnetic recording medium 10 is preferably 220 kA/m to310 kA/m, more preferably 230 kA/m to 300 kA/, still more preferably 240kA/m to 290 kA/m. When the coercive force Hc is 220 kA/m or more, thecoercive force Hc becomes a sufficient magnitude, and thus, adegradation of a magnetic signal recorded on an adjacent track due to aleakage magnetic field from the recording head may be suppressed.Therefore, a better SNR can be obtained. On the other hand, when thecoercive force Hc is 310 kA/m or less, saturation recording by therecording head is facilitated, and thus, a better SNR can be obtained.

The coercive force Hc is obtained as follows. First, a measurementsample is cut out from the long-shaped magnetic recording medium 10 andan M-H loop of the entire measurement sample is measured in thethickness direction of the measurement sample (thickness direction ofthe magnetic recording medium 10) using a vibrating sample magnetometer(VSM). Next, the coating film (ground layer 12, magnetic layer 13, etc.)is wiped out using acetone, ethanol, or the like, to leave only the baselayer 11 for background correction, and the M-H loop of the base layer11 is measured in the thickness direction of the base layer 11 (thethickness direction of the magnetic recording medium 10) using the VSM.Thereafter, the M-H loop of the base layer 11 is subtracted from the M-Hloop of the entire measurement sample to obtain an M-H loop afterbackground correction. The coercive force Hc is obtained from theobtained M-H loop. Note that it is assumed that the measurement of theM-H loop is entirely performed at 25° C. Furthermore, it is also assumedthat “demagnetizing field correction” when the M-H loop is measured inthe thickness direction (vertical direction) of the magnetic recordingmedium 10 is not performed.

(Ratio R of Coercive Force Hc(50) and Coercive Force Hc(25))

The ratio R (=(Hc(50)/Hc(25))×100) between the coercive force Hc(50)measured at 50° C. in the thickness direction (vertical direction) ofthe magnetic recording medium 10 to the coercive force Hc(25) measuredat 25° C. in the thickness direction of the magnetic recording medium 10is preferably 95% or more, more preferably 96% or more, still morepreferably 97% or more, and particularly preferably 98% or more. Whenthe ratio R is 95% or more, temperature dependence of the coercive forceHc is small, and thus, deterioration of the SNR under a high temperatureenvironment can be suppressed.

The coercive force Hc(25) is obtained in a manner similar to the methodof measuring the coercive force Hc. Furthermore, the coercive forceHc(50) is obtained in a manner similar to the method of measuring thecoercive force Hc except that the M-H loops of the measurement sampleand the base layer 11 are all measured at 50° C.

(Squareness Ratio S1 Measured in Longitudinal Direction)

The squareness ratio S1 measured in the longitudinal direction (runningdirection) of the magnetic recording medium 10 is preferably 35% orless, more preferably 27% or less, and still more preferably 20% orless. When the squareness ratio S1 is 35% or less, vertical alignment ofthe magnetic powder is sufficiently high, and therefore, a better SNRcan be obtained. Therefore, better electromagnetic conversioncharacteristic can be obtained. Furthermore, a shape of the servo signalis improved, and thus, the control on the drive side may be performedmore easily.

In this specification, the perpendicular alignment of the magneticrecording medium may mean that the squareness ratio S1 of the magneticrecording medium is within the above numerical range (for example, 35%or less). The magnetic recording medium according to the embodiment ofthe present technology is preferably perpendicularly aligned.

The squareness ratio S1 is obtained as follows. First, a measurementsample is cut out from a long-shaped magnetic recording medium 10, andan M-H loop of the entire measurement sample corresponding to thelongitudinal direction (running direction) of the magnetic recordingmedium 10 is measured using the VSM. Next, the coating film (groundlayer 12, magnetic layer 13, etc.) is wiped out using acetone, ethanol,or the like, to leave only the base layer 11 for background correction,and the M-H loop of the base layer 11 corresponding to the longitudinaldirection of the base layer 11 (running direction of the magneticrecording medium 10) is measured using the VSM. Thereafter, the M-H loopof the base layer 11 is subtracted from the M-H loop of the entiremeasurement sample to obtain an M-H loop after background correction.The squareness ratio S1(%) is calculated by substituting a saturationmagnetization Ms(emu) and residual magnetization Mr(emu) of the obtainedM-H loop into the following equation. Note that it is assumed that themeasurement of the M-H loop is entirely performed at 25° C.Squareness ratio S1(%)=(Mr/Ms)×100

(Squareness Ratio S2 Measured in Vertical Direction)

The squareness ratio S2 measured in the vertical direction (thicknessdirection) of the magnetic recording medium 10 is preferably 65% ormore, more preferably 73% or more, and still more preferably 80% ormore. When the squareness ratio S2 is 65% or more, vertical alignment ofthe magnetic powder is sufficiently high, and thus, a better SNR can beobtained. Therefore, better electromagnetic conversion characteristiccan be obtained. Furthermore, a servo signal shape is improved, makingit easier to control a drive side.

In this specification, the perpendicular alignment of the magneticrecording medium may mean that the squareness ratio S2 of the magneticrecording medium is within the above numerical range (for example, 65%or more).

The squareness ratio S2 is obtained in a similar manner to thesquareness ratio S1 except that the M-H loops are measured in thevertical direction (thickness direction) of the magnetic recordingmedium 10 and the base layer 11. Note that, in the measurement of thesquareness ratio S2, it is assumed that “demagnetizing field correction”when measuring the M-H loop is measured in the vertical direction of themagnetic recording medium 10 is not performed.

The squareness ratios S1 and S2 may be set to a desired value byadjusting, for example, strength of a magnetic field applied to themagnetic layer forming coating material, an application time of themagnetic field to the magnetic layer forming coating material, adispersion state of the magnetic powder in the magnetic layer formingcoating material, and a concentration of the solid content in themagnetic layer forming coating material. Specifically, for example, asthe strength of the magnetic field is increased, the squareness ratio S1is reduced, while the squareness ratio S2 is increased. Furthermore, asthe application time of the magnetic field is longer, the squarenessratio S1 is reduced, while the squareness ratio S2 is increased.Furthermore, as the dispersion state of the magnetic powder is improved,the squareness ratio S1 is reduced, while the squareness ratio S2 isincreased. Furthermore, as the concentration of the solid content islowered, the squareness ratio S1 is reduced, while the squareness ratioS2 is increased. Note that the above adjustment method may be used aloneor in combination of two or more.

(SFD)

In a switching field distribution (SFD) curve of the magnetic recordingmedium 10, a peak ratio X/Y of a main peak height X and a height Y of asub peak in the vicinity of magnetic field zero is preferably 3.0 ormore, more preferably 5.0 or more, still more preferably 7.0 or more,particularly preferably 10.0 or more, and most preferably 20.0 or more(see FIG. 4). When the peak ratio X/Y is 3.0 or more, it is possible tosuppress inclusion of a large amount of coercive force component (forexample, soft magnetic particles, superparamagnetic particles, etc.)unique to ε iron oxide other than the ε iron oxide particlescontributing to actual recording in the magnetic powder. Therefore,deterioration of magnetization signals recorded on the adjacent tracksdue to a leakage magnetic field from the recording head is suppressed,and thus, a better SNR can be obtained. An upper limit value of the peakratio X/Y is not particularly limited, but is, for example, 100 or less.

The peak ratio X/Y is obtained as follows. First, an M-H loop afterbackground correction is obtained in a manner similar to the method ofmeasuring the coercive force Hc described above. Next, an SFD curve iscalculated from the obtained M-H loop. The calculation of the SFD curvemay be performed by using a program attached to the measurement device,or by using other programs. Assuming that an absolute value of a pointat which the calculated SFD curve traverses the Y axis (dM/dH) is “Y”and a height of the main peak seen in the vicinity of the coercive forceHc in the M-H loop is “X”, a peak ratio X/Y is calculated. Note that themeasurement of the M-H loop is performed at 25° C. in a manner similarto the method of measuring the coercive force Hc described above.Furthermore, it is also assumed that “demagnetizing field correction”when the M-H loop is measured in the thickness direction (verticaldirection) of the magnetic recording medium 10 is not performed.

(Activation Volume V_(act))

The activation volume V_(act) is preferably 8000 nm³ or less, morepreferably 6000 nm³ or less, still more preferably 5000 nm³ or less,particularly preferably 4000 nm³ or less, and most preferably 3000 nm3or less. When the activation volume V_(act) is 8000 nm³ or less, thedispersion state of the magnetic powder is improved, and thus, a bitreversal region can be made steep and a degradation of the magnetizationsignal recorded on the adjacent track due to a leakage magnetic fieldfrom the recording head may be suppressed. Therefore, there is apossibility that a better SNR may not be obtained.

The activation volume V_(act) is obtained by the following equationderived by Street&Woolley.V _(act) (nm³)=k _(B) ×T×X _(irr)/(μ₀ ×Ms×S)

(where, kB: Boltzmann constant (1.38×10⁻²³ J/K), T: temperature (K),X_(irr):

-   -   irreversible magnetic susceptibility, μ₀: permeability of        vacuum, S: magnetic viscosity coefficient, Ms: saturation        magnetization (emu/cm3))

The irreversible magnetic susceptibility X_(irr), the saturationmagnetization Ms and the magnetic viscosity coefficient S substituted inthe above equation are obtained as follows using the VSM. Note that themeasurement direction by the VSM is the thickness direction (verticaldirection) of the magnetic recording medium 10. Furthermore, it isassumed that the measurement by the VSM is performed at 25° C. for themeasurement sample cut out from the long-shaped magnetic recordingmedium 10. Furthermore, it is also assumed that “demagnetizing fieldcorrection” when the M-H loop is measured in the thickness direction(vertical direction) of the magnetic recording medium 10 is notperformed.

(Irreversible Magnetic Susceptibility X_(irr))

The irreversible magnetic susceptibility X_(irr) is defined as aninclination in the vicinity of the residual coercive force Hr in theinclination of the residual magnetization curve (DCD curve). First, amagnetic field of −1193 kA/m (15 kOe) is applied to the entire magneticrecording medium 10, and the magnetic field is returned to zero to entera residual magnetization state. Thereafter, a magnetic field of about15.9 kA/m (200 Oe) is applied in the opposite direction, and themagnetic field is returned again to zero and a residual magnetizationamount is measured. Thereafter, similarly, a measurement of applying amagnetic field 15.9 kA/m larger than the immediately previously appliedmagnetic field and returning the magnetic field to zero is repeatedlyperformed, and a DCD curve is measured by plotting a residualmagnetization amount against the applied magnetic field. From theobtained DCD curve, the point at which the magnetization amount is zerois set as the residual coercive force Hr, and an inclination of the DCDcurve in each magnetic field is obtained by differentiating the DCDcurve again. In the inclination of the DCD curve, the inclination nearthe residual coercive force Hr is X_(irr).

(Saturation Magnetization Ms)

First, an M-H loop of the entire magnetic recording medium 10(measurement sample) is measured in the thickness direction of themagnetic recording medium 10. Next, the coating film (ground layer 12,magnetic layer 13, etc.) is wiped out using acetone, ethanol, or thelike, to leave only the base layer 11 for background correction, and theM-H loop of the base layer 11 is measured in the thickness direction ofthe base layer 11 similarly. Thereafter, the M-H loop of the base layer11 is subtracted from the M-H loops of the entire magnetic recordingmedium 10 to obtain an M-H loop after background correction. Ms(emu/cm³) is calculated from the value of the saturation magnetizationMs (emu) of the obtained M-H loop and the volume (cm³) of the magneticlayer 13 in the measurement sample. Note that the volume of the magneticlayer 13 is obtained by multiplying the area of the measurement sampleby the average thickness of the magnetic layer 13. A method ofcalculating the average thickness of the magnetic layer 13 necessary forcalculating the volume of the magnetic layer 13 will be described later.

(Magnetic Viscosity Coefficient S)

First, a magnetic field of −1193 kA/m (15 kOe) is applied to the entiremagnetic recording medium 10 (measurement sample), and the magneticfield is returned to zero to enter a residual magnetization state.Thereafter, in the opposite direction, a magnetic field equivalent tothe value of the residual coercive force Hr obtained from the DCD curveis applied. With the magnetic field applied, the magnetization amount iscontinuously measured at constant time intervals for 1000 seconds. Arelationship between the time t and the magnetization amount M(t) thuslyobtained is compared with the following equation to calculate themagnetic viscosity coefficient S.M(t)=M0+S×ln(t)

(where M(t): magnetization amount at time t, M0: initial magnetizationamount, S: magnetic viscosity coefficient, ln(t): natural logarithm oftime)

(Arithmetic Mean Roughness Ra)

The arithmetic mean roughness Ra of the magnetic surface is preferably2.5 nm or less, and more preferably 2.0 nm or less. When Ra is 2.5 nm orless, a better SNR can be obtained.

The arithmetic mean roughness Ra is obtained as follows. First, thesurface of the side on which the magnetic layer 13 is provided isobserved using an atomic force microscope (AFM) (Dimension Iconmanufactured by Bruker Corporation) to obtain a cross-sectional profile.Next, the arithmetic mean roughness Ra is obtained from the obtainedcross-sectional profile in accordance with JIS B0601: 2001.

(4) Method of Manufacturing Magnetic Recording Medium

Next, a method of manufacturing the magnetic recording medium 10 havingthe above-described configuration will be described. First, a groundlayer-forming coating material is prepared by kneading and/or dispersinga non-magnetic powder, a binder, or the like, in a solvent. Next, themagnetic layer-forming coating material is prepared by kneading and/ordispersing the magnetic powder and the binder in a solvent. For thepreparation of the magnetic layer-forming coating material and theground layer-forming coating material, for example, the followingsolvents, a dispersing device and a kneading device may be used.

Examples of the solvents used for preparing the above-described coatingmaterial include ketone solvents such as acetone, methyl ethyl ketone,methyl isobutyl ketone, cyclohexanone, and the like; alcohol solventssuch as methanol, ethanol and propanol; ester solvents such as methylacetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate,ethylene glycol acetate, and the like; ether solvents such as diethyleneglycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, dioxane, andthe like; aromatic hydrocarbon solvents such as benzene, toluene andxylene; and halogenated hydrocarbon solvents such as methylene chloride,ethylene chloride, carbon tetrachloride, chloroform, chlorobenzene, andthe like. One of these may be used, or a mixture of two or more thereofmay be used.

As the kneading device used in the preparation of the coating materialpreparation described above, for example, a kneading device such as acontinuous biaxial kneader, a continuous biaxial kneader capable ofdiluting in multiple steps, a kneader, a press kneader, and a rollkneader may be used but the present technology is not particularlylimited thereto. Furthermore, examples of the dispersing device used inthe preparation of the coating material preparation described aboveinclude roll mills, ball mills, horizontal sand mills, vertical sandmills, spike mills, pin mills, tower mills, pearl mills (for example,DCP Mill, manufactured by Nippon Eirich Co., Ltd., etc.), a homogenizer,an ultrasonic dispersing device, or the like, may be used, but thepresent technology is not particularly limited thereto.

Next, the ground layer-forming coating material is applied to one mainsurface of the base layer 11 and dried to form the ground layer 12.Subsequently, the magnetic layer-forming coating material is applied tothe ground layer 12 and dried to form the magnetic layer 13 on theground layer 12. Note that, at the time of drying, magnetic powder ismagnetically aligned in the thickness direction of the base layer 11 by,for example, a solenoid coil. Furthermore, at the time of drying, forexample, the magnetic powder may be magnetically aligned in thelongitudinal direction (running direction) of the base layer 11 and thenmagnetically aligned in the thickness direction of the base layer 11 bya solenoid coil. After the formation of the magnetic layer 13, the backlayer 14 is formed on the other main surface of the base layer 11.Accordingly, the magnetic recording medium 10 is obtained.

Thereafter, the obtained magnetic recording medium 10 is wound around alarge-diameter core again and a curing treatment is performed thereon.Finally, calendering is performed on the magnetic recording medium 10,and thereafter, the magnetic recording medium 10 is cut into apredetermined width (for example, ½ inch width). As a result, a magneticrecording medium 10 of a desired long shape may be obtained.

(5) Recording and Reproducing Apparatus

[Configuration of Recording and Reproducing Apparatus]

Next, an example of a configuration of a recording and reproducingapparatus 30 that performs recording and reproducing of the magneticrecording medium 10 accommodated in the magnetic recording cartridge 1having the above-described configuration will be described withreference to FIG. 5.

The recording and reproducing apparatus 30 has a configuration capableof adjusting tension applied in the longitudinal direction of themagnetic recording medium 10. Furthermore, the recording and reproducingapparatus 30 has a configuration allowing the magnetic recordingcartridge 1 to be loaded therein. Here, in order to facilitate thedescription, a case where the recording and reproducing apparatus 30 hasa configuration allowing one magnetic recording cartridge 1 to be loadedtherein will be described, but the recording and reproducing apparatus30 may be configured so that a plurality of magnetic recordingcartridges 1 may be loaded therein.

The recording and reproducing apparatus 30 is preferably a timing servotype magnetic recording and reproducing apparatus. The magneticrecording medium according to the embodiment of the present technologyis suitable for use in a timing servo type magnetic recording andreproducing apparatus.

The recording and reproducing apparatus 30 is connected to aninformation processing device such as a server 41 and a personalcomputer (hereinafter referred to as “PC”) 42 via a network 43, and isconfigured to record data supplied from these information processingdevices in the magnetic recording medium 10 in the magnetic recordingcartridge 1. The shortest recording wavelength of the recording andreproducing apparatus 30 is preferably 100 nm or less, more preferably75 nm or less, still more preferably 60 nm or less, and particularlypreferably 50 nm or less.

As illustrated in FIG. 5, the recording and reproducing apparatusincludes a spindle 31, a reel 32 on the recording and reproducingapparatus side, a spindle driving device 33, a reel driving device 34, aplurality of guide rollers 35, a head unit 36, a communication interface(I/F) 37, and a control device 38.

The spindle 31 is configured to mount the magnetic recording cartridge1. The magnetic recording cartridge 1 is compliant with the linear tapeopen (LTO) standard and accommodates a single reel 3, around which themagnetic recording medium 10 is wound, mounted in the cartridge case 2.In the magnetic recording medium 10, an inverted V-shaped servo patternis recorded in advance as a servo signal. The reel 32 is configured tofix a leading end of the magnetic recording medium 10 drawn out from themagnetic recording cartridge 1.

The spindle driving device 33 is a device for rotationally driving thespindle 31. The reel driving device 34 is a device for rotationallydriving the reel 32. When data is recorded to or reproduced from themagnetic recording medium 10, the spindle driving device 33 and the reeldriving device 34 rotationally drive the spindle 31 and the reel 32 tocause the magnetic recording medium 10 to run. The guide roller 35 is aroller for guiding running of the magnetic recording medium 10.

The head unit 36 includes a plurality of recording heads for recordingdata signals to the magnetic recording medium 10, a plurality ofreproducing heads for reproducing the data signals recorded on themagnetic recording medium 10, and a plurality of servo heads forreproducing a servo signal recorded on the magnetic recording medium 10.As the recording head, for example, a ring type head may be used, butthe type of the recording head is not limited thereto.

The communication I/F 37 is for communicating with the informationprocessing device such as the server 41 and the PC 42, and is connectedto the network 43.

The control device 38 controls the entire recording and reproducingapparatus 30. For example, the control device 38 records the data signalsupplied from the information processing device such as the server 41 orthe PC 42 to the magnetic recording medium 10 by the head unit 36 inresponse to a request from the information processing device.Furthermore, the control device 38 reproduces the data signal recordedon the magnetic recording medium 10 by the head unit 36 and supplies thereproduced data signal to the information processing apparatus, inresponse to the request from the information processing apparatus suchas the server 41 and the PC 42.

Furthermore, the control device 38 detects a change in width of themagnetic recording medium 10 on the basis of the servo signal suppliedfrom the head unit 36. More specifically, the magnetic recording medium10 has a plurality of inverted V-shaped servo patterns recorded as servosignals thereon and the head unit 36 simultaneously reproduces twodifferent servo patterns by the two servo heads on the head unit 36 andobtain each servo signal. A position of the head unit 36 is controlledto follow the servo pattern using the servo pattern and relativeposition information of the head unit obtained from this servo signal.At the same time, distance information between the servo patterns may beobtained by comparing the two servo signal waveforms. By comparing thedistance information between the servo patterns obtained at the time ofeach measurement, a change in distance between the servo patterns at thetime of each measurement may be obtained. By adding the distanceinformation between the servo patterns at the time of servo patternrecording, a change in the width of the magnetic recording medium 10 mayalso be calculated. The control device 38 adjusts tension in alongitudinal direction of the magnetic recording medium 10 so that thewidth of the magnetic recording medium 10 is a defined width or asubstantially defined width by controlling rotation driving of thespindle driving device 33 and the reel driving device 34 on the basis ofthe change in the distance between the servo patterns obtained asdescribed above or the calculated width of the magnetic recording medium10. Accordingly, a change in the width of the magnetic recording medium10 may be suppressed.

[Operation of Recording and Reproducing Apparatus]

Next, the operation of the recording and reproducing apparatus 30 havingthe above-described configuration will be described.

First, the magnetic recording cartridge 1 is attached to the recordingand reproducing apparatus 30, a leading end of the magnetic recordingmedium 10 is drawn out and transferred to the reel 32 through theplurality of guide rollers 35 and the head unit 36, and the leading endof the magnetic recording medium 10 is installed on the reel 32.

Next, when an operation unit (not shown) is operated, the spindledriving device 33 and the reel driving device 34 are driven under thecontrol of the control device 38, and the spindle 31 and the reel 32 arerotated in the same direction so that the magnetic recording medium 10runs from the reel 3 toward the reel 32. As a result, while the magneticrecording medium 10 is being wound around the reel 32, information isrecorded on the magnetic recording medium 10 or information recorded onthe magnetic recording medium 10 is reproduced by the head unit 36.

Furthermore, in a case where the magnetic recording medium 10 is rewoundaround the reel 3, the spindle 31 and the reel 32 are rotationallydriven in a direction opposite to the above direction such that themagnetic recording medium 10 runs from the reel 32 to the reel 3. Also,at the time of rewinding, the information is recorded on the magneticrecording medium 10 or the information recorded on the magneticrecording medium 10 is reproduced by the head unit 36.

(6) Effect

The magnetic recording medium 10 included in the magnetic recordingcartridge according to the first embodiment has an average thicknesst_(T) of t_(T)≤5.6 μm and a dimensional change amount Δw of 660 ppm/N≤Δwin a width direction of the magnetic recording medium 10 with respect toa change in tension in the longitudinal direction of the magneticrecording medium 10, and a squareness ratio of 65% or more in a verticaldirection. As a result, a recording capacity per cartridge is high, anda

change in the width of the magnetic recording medium 10 may besuppressed by adjusting tension in the longitudinal direction of themagnetic recording medium 10 by the recording and reproducing apparatus.

Moreover, the magnetic recording medium 10 is accommodated in a state ofbeing wound around a reel and (servo track width on inner side ofwinding of magnetic recording medium)−(servo track width on outer sideof winding of magnetic recording medium)>0 is satisfied. As a result,the occurrence of wrinkles on the inner side of winding in the cartridgemay be suppressed.

As described above, the magnetic recording cartridge according to thefirst embodiment has high recording capacity per cartridge, is suitablefor use in a recording and reproducing apparatus which adjusts tensionin the longitudinal direction of the magnetic recording medium, andsuppresses the occurrence of wrinkles that may occur with the tensionadjustment.

(7) Modification Modification 1

The magnetic recording medium 10 may further include a barrier layer 15provided on at least one surface of the base layer 11 as shown in FIG.7. The barrier layer 15 is a layer for suppressing a dimensional changein the base layer 11 depending on the environment. For example, moistureabsorbency of the base layer 11 is an example of a cause of thedimensional change, and a penetration speed of moisture into the baselayer 11 may be reduced by the barrier layer 15. The barrier layer 15includes a metal or a metal oxide. As the metal, for example, at leastone of Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo,Ru, Pd, Ag, Ba, Pt, Au, or Ta may be used. As the metal oxide, forexample, at least one of Al₂O₃, CuO, CoO, SiO₂, Cr₂O₃, TiO₂, Ta₂O₅ orZrO₂ may be used, and any of the oxides of the above metals may also beused. Furthermore, diamond-like carbon (DLC), diamond, and the like mayalso be used.

An average thickness of the barrier layer 15 is preferably 20 nm to 1000nm, and more preferably 50 nm to 1000 nm. The average thickness of thebarrier layer 15 is obtained in a manner similar to the averagethickness t_(m) of the magnetic layer 13. However, a magnification ofthe TEM image is appropriately adjusted according to thicknesses of thebarrier layer 15.

Modification 2

The magnetic recording medium 10 may be incorporated in a libraryapparatus. In other words, the present technology also provides alibrary apparatus including at least one magnetic recording medium 10.The library apparatus has a configuration capable of adjusting tensionapplied in the longitudinal direction of the magnetic recording medium10, and may include a plurality of the recording and reproducingapparatuses 30 described above.

Modification 3

The magnetic recording medium 10 may be attached to servo signal writeprocessing by a servo writer. The servo writer may adjust tension in thelongitudinal direction of the magnetic recording medium 10 whenrecording a servo signal or the like, thereby keeping the width of themagnetic recording medium 10 constant or substantially constant. In thiscase, the servo writer may have a detection device for detecting thewidth of the magnetic recording medium 10. The servo writer may adjustthe tension in the longitudinal direction of the magnetic recordingmedium 10 on the basis of a detection result from the detection device.

3. SECOND EMBODIMENT (EXAMPLE OF MAGNETIC RECORDING CARTRIDGE INCLUDINGVACUUM THIN FILM TYPE MAGNETIC RECORDING MEDIUM) (1) Configuration ofMagnetic Recording Cartridge

The magnetic recording cartridge of the present embodiment is the sameas the magnetic recording cartridge 1 described in “(1) Configuration ofmagnetic cartridge” of 2. except that a vacuum thin-film type magneticrecording medium 110 is used instead of the coating type magneticrecording medium 10. Hereinafter, the vacuum thin-film type magneticrecording medium 110 will be described.

The magnetic recording medium 110 is a long, vertical magnetic recordingmedium and includes a film type base layer 111, a soft magneticunderlayer 112 (hereinafter referred to as SUL), a first seed layer113A, a second seed layer 113B, a first ground layer 114A, a secondground layer 114B, and a magnetic layer 115 as illustrated in FIG. 8.The SUL 112, the first and second seed layers 113A and 113B, first andsecond ground layers 114A and 114B, and the magnetic layer 115 may be,for example, vacuum thin films such as layers formed by sputtering(hereinafter also referred to as “sputtered layer”), or the like.

The SUL 112, the first and second seed layers 113A and 113B, and thefirst and second ground layer 114A and 114B are provided between onemain surface of the base layer 111 (hereinafter referred to as“surface”) and the magnetic layer 115, and the SUL 112, the first seedlayer 113A, the second seed layer 113B, the first ground layer 114A, andthe second ground layer 114B are stacked in this order from the baselayer 111 toward the magnetic layer 115.

The magnetic recording medium 110 may further include a protective layer116 provided on the magnetic layer 115 and a lubricating layer 117provided on the protective layer 116 as necessary. Furthermore, themagnetic recording medium 110 may further include a back layer 118provided on the other main surface (hereinafter referred to as “backsurface”) of the base layer 111 as necessary.

Hereinafter, the longitudinal direction of the magnetic recording medium110 (longitudinal direction of the base layer 111) is referred to as amachine direction (MD). Here, the machine direction refers to a relativemovement direction of a recording and reproducing head with respect tothe magnetic recording medium 110, that is, the direction in which themagnetic recording medium 110 runs at the time of recording andreproduction.

The magnetic recording medium 110 is preferably used as a storage mediumfor a data archive, which is expected to increase in demand in thefuture. This magnetic recording medium 110 may realize a surfacerecording density of 10 times or more, that is, a surface recordingdensity of 50 Gb/in² or more, for example, of the current coating typemagnetic recording medium for storage. In a case where a general linearrecording type data cartridge is configured using the magnetic recordingmedium 110 having such a surface recording density, a large capacityrecording of 100 TB or more per data cartridge may be realized.

The magnetic recording medium 110 is preferably used in a recording andreproducing apparatus (recording and reproducing apparatus for recordingand reproducing data) having a ring-type recording head and a giantmagnetoresistive (GMR) type reproducing head or a tunnelingmagnetoresistive (TMR) type reproducing head. Furthermore, it ispreferable that the magnetic recording medium 110 according to thesecond embodiment uses a ring-type recording head as the servo signalwrite head. In the magnetic layer 115, for example, a data signal isvertically recorded by a ring-type recording head. Furthermore, in themagnetic layer 115, for example, a servo signal is vertically recordedby the ring-type recording head.

(2) Description of Each Layer

(Base Layer)

The description regarding the base layer 11 in the first embodiment isapplied to the base layer 111, and a description regarding the baselayer 111 is thus omitted.

(SUL)

The SUL 112 contains a soft magnetic material in an amorphous state. Thesoft magnetic material includes, for example, at least one of a Co-basedmaterial or an Fe-based material. The Co-based material includes, forexample, CoZrNb, CoZrTa, or CoZrTaNb. The Fe-based material includes,for example, FeCoB, FeCoZr, or FeCoTa.

The SUL 112 is a single-layer SUL, and is provided directly on the baselayer 111. An average thickness of the SUL 112 is preferably 10 nm ormore to 50 nm or less, and more preferably 20 nm or more and 30 nm orless.

The average thickness of the SUL 112 is obtained by the same method asthe method of measuring the average thickness of the magnetic layer 13in the first embodiment. Note that average thicknesses of layers otherthan the SUL 112, as described later (in other words, averagethicknesses of first and second seed layers 113A and 113B, first andsecond ground layers 114A and 114B, and a magnetic layer 115) are alsoobtained by the same method as the method of measuring the averagethickness of the magnetic layer 13 in the first embodiment. However, amagnification of a TEM image is appropriately adjusted according to thethickness of each layer.

(First and Second Seed Layers)

The first seed layer 113A contains an alloy containing Ti and Cr, andhas an amorphous state. Furthermore, this alloy may further contain O(oxygen). The oxygen may be impurity oxygen contained in a small amountin the first seed layer 113A when the first seed layer 113A is formed bya film forming method such as a sputtering method or the like.

Here, the “alloy” means at least one of a solid solution, a eutecticmaterial, an intermetallic compound, or the like, containing Ti and Cr.The “amorphous state” means a state in which a halo is observed by X-raydiffraction, electron beam diffraction method or the like, and a crystalstructure may not be specified.

An atomic ratio of Ti to a total amount of Ti and Cr contained in thefirst seed layer 113A is preferably 30 atomic % or more and less than100 atomic %, and more preferably 50 atomic % or more and less than 100atomic %. When the atomic ratio of Ti is less than 30 atomic %, a (100)plane of a body-centered cubic lattice (bcc) structure of Cr is aligned,so that there is a possibility that alignment of the first and secondground layers 114A and 114B formed on the first seed layer 113A will bereduced.

The atomic ratio of Ti is obtained as follows. Depth direction analysis(depth profile measurement) of the first seed layer 113A by augerelectron spectroscopy (hereinafter referred to as “AES”) is performedwhile ion-milling the magnetic recording medium 110 from the magneticlayer 115 side. Next, an average composition (average atomic ratio) ofTi and Cr in the film thickness direction is obtained from the obtaineddepth profile. Next, the atomic ratio of Ti is obtained using theobtained average composition of Ti and Cr.

In a case where the first seed layer 113A contains Ti, Cr and O, anatomic ratio of 0 to a total amount of Ti, Cr and O contained in thefirst seed layer 113A is preferably 15 atomic % or less, and morepreferably Is 10 atomic % or less. In a case where the atomic ratio of Oexceeds 15 atomic %, TiO₂ crystals are formed, which affects nucleationof the first and second ground layers 114A and 114B formed on the firstseed layer 113A, so that there is a possibility that the alignment ofthe first and second ground layers 114A and 114B will be reduced. Theatomic ratio of O is obtained using a method similar to a method ofanalyzing the atomic ratio of Ti.

The alloy contained in the first seed layer 113A may further contain anelement other than Ti and Cr as an additional element. This additionalelement may be, for example, one or more elements selected from thegroup including Nb, Ni, Mo, Al, and W.

The average thickness of the first seed layer 113A is preferably 2 nm to15 nm, and more preferably 3 nm to 10 m.

The second seed layer 113B contains, for example, NiW or Ta, and has acrystalline state. The average thickness of the second seed layer 113Bis preferably 3 nm to 20 nm, and more preferably 5 nm to 15 nm.

The first and second seed layers 113A and 113B have a crystal structuresimilar to that of the first and second ground layers 114A and 114B, andare not seed layers provided for the purpose of crystal growth, but areseed layers improving vertical alignment of the first and second groundlayers 114A and 114B by amorphous states of the first and second seedlayers 113A and 113B.

(First and Second Ground Layers)

It is preferable that the first and second ground layers 114A and 114Bhave a crystal structure similar as that of the magnetic layer 115. In acase where the magnetic layer 115 contains a Co-based alloy, it ispreferable that the first and second ground layers 114A and 114B containa material having a hexagonal closest-packed (hcp) structure similar tothat of the Co-based alloy and a c axis of the hcp structure is alignedin a direction (that is, film thickness direction) perpendicular to afilm surface. The reason is because the alignment of the magnetic layer115 can be improved and matching in a lattice constant between thesecond ground layer 114B and the magnetic layer 115 can be maderelatively good. As the material having the hexagonal closest-packed(hcp) structure, it is preferable to use a material containing Ru, andspecifically, it is preferable to use Ru alone or use a Ru alloy.Examples of the Ru alloy can include Ru alloy oxides such as Ru—SiO₂,Ru—TiO₂, Ru—ZrO₂, and the like, and the Ru alloy may be any one ofRu—SiO₂, Ru—TiO₂, and Ru—ZrO₂.

As described above, similar materials can be used as the materials ofthe first and second ground layers 114A and 114B. However, intendedeffects of each of the first and second ground layers 114A and 114B aredifferent from each other. Specifically, the second ground layer 114Bhas a film structure promoting a granular structure of the magneticlayer 115 which is an upper layer of the second ground layer 114B, andthe first ground layer 114A has a film structure with a high crystalalignment. In order to obtain such a film structure, it is preferablethat film forming conditions such as sputtering conditions or the likeof each of the first and second ground layers 114A and 114B are made tobe different from each other.

The average thickness of the first ground layer 114A is preferably 3 nmto 15 nm or less, and more preferably 5 nm to 10 nm. The averagethickness of the second ground layer 114B is preferably 7 nm to 40 nm,and more preferably 10 nm to 25 nm.

(Magnetic Layer)

The magnetic layer (also referred to as a recording layer) 115 may be avertical magnetic recording layer in which a magnetic material isvertically aligned. It is preferable that the magnetic layer 115 is agranular magnetic layer containing a Co-based alloy, in terms ofimprovement of a recording density. The granular magnetic layer containsferromagnetic crystal particles containing the Co-based alloy andnonmagnetic grain boundaries (nonmagnetic material) surrounding theferromagnetic crystal particles. More specifically, the granularmagnetic layer contains columns (columnar crystal) containing a Co-basedalloy and nonmagnetic grain boundaries (for example, oxides such asSiO₂) surrounding the columns and magnetically separating the respectivecolumns from each other. In this structure, the magnetic layer 115having a structure in which the respective columns are magneticallyseparated from each other may be configured.

The Co-based alloy has a hexagonal closest-packed (hcp) structure, and ac-axis of the hcp structure is aligned in the direction (film thicknessdirection) perpendicular to the film surface. As the Co-based alloy, itis preferable to use a CoCrPt-based alloy containing at least Co, Cr,and Pt. The CoCrPt-based alloy may further contain an additive element.Examples of the additive element can include one or more elementsselected from the group including Ni and Ta.

The nonmagnetic grain boundaries surrounding the ferromagnetic crystalgrains contain a nonmagnetic metallic material. Here, the metal includesa metalloid. As the nonmagnetic metal material, for example, at leastone of a metal oxide or a metal nitride can be used, and it ispreferable to use the metal oxide, in terms of more stable maintenanceof the granular structure. Examples of the metal oxide can include metaloxides containing one or more elements selected from the group includingSi, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, Hf, and the like, and the metal oxideis preferably a metal oxide including at least Si oxide (that is, SiO₂).Specific examples of the metal oxide can include SiO₂, Cr₂O₃, CoO,Al₂O₃, TiO₂, Ta₂O₅, ZrO₂, HfO₂, and the like. Examples of the metalnitride can include metal nitrides containing one or more elementsselected from the group including Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, Hf,and the like. Specific examples of the metal nitride can include SiN,TiN, AlN, and the like.

It is preferable that the CoCrPt-based alloy contained in theferromagnetic crystal particle and the Si oxide contained in thenonmagnetic grain boundary have an average composition represented inthe following Formula (1). The reason is because a saturationmagnetization amount Ms in which an influence of a demagnetizing fieldcan be suppressed and a sufficient reproduction output can be obtainedcan be realized, resulting in further improvement of recording andreproduction characteristics.(Co_(x)Pt_(y)Cr_(100-x-y))_(100-z-)(SiO₂)_(z)  (1)

(where in General Formula (1), x, y, and z are values within ranges inwhich 69≤x≤75, 10≤y≤16, and 9≤Z≤12 are satisfied, respectively).

Note that the above composition can be obtained as follows. An averagecomposition (average atomic ratio) of Co, Pt, Cr, Si, and O in the filmthickness direction is obtained by performing the depth directionanalysis on the magnetic layer 115 by the AES while ion-milling themagnetic recording medium 110 from the magnetic layer 115 side.

An average thickness t_(m) [nm] of the magnetic layer 115 is preferably9 nm≤t_(m)≤90 nm, more preferably 9 nm≤t_(m)≤20 nm, and still morepreferably 9 nm≤t_(m)≤15 nm. The average thickness t_(m) of the magneticlayer 13 is within the above numerical range, so that electromagneticconversion characteristics can be improved.

(Protective Layer)

The protective layer 116 contains, for example, a carbon material orsilicon dioxide (SiO2), and it is preferable that the protective layer116 contains a carbon material in view of film strength of theprotective layer 116. Examples of the carbon material include graphite,diamond-like carbon (DLC), diamond, or the like.

(Lubricating Layer)

The lubricating layer 117 contains at least one lubricant. Thelubricating layer 117 may further contain various additives, forexample, a rust inhibitor, as necessary. A lubricant has at least twocarboxyl groups and one ester bond, and contains at least one ofcarboxylic acid-based compounds represented by the following GeneralFormula (1). The lubricant may further contain a lubricant other thanthe carboxylic acid-based compound represented by the following GeneralFormula (1).

General Formula (1):

(where, Rf is an unsubstituted or substituted saturated or unsaturatedfluorine-containing hydrocarbon group or a hydrocarbon group, Es is anester bond, R may be absent, but is an unsubstituted or substitutedsaturated or unsaturated hydrocarbon group).

It is preferable that the carboxylic acid-based compound is representedby the following General Formula (2) or (3).

General Formula (2):

(where, Rf is an unsubstituted or substituted saturated or unsaturatedfluorine-containing hydrocarbon group or a hydrocarbon group).

General Formula (3):

(where, Rf is an unsubstituted or substituted saturated or unsaturatedfluorine-containing hydrocarbon group or a hydrocarbon group).

It is preferable that the lubricant contains one or both of thecarboxylic acid-based compound represented by the above General Formulas(2) and (3).

When the lubricant containing the carboxylic acid-based compoundrepresented by General Formula (1) is coated on the magnetic layer 115,the protective layer 116 or the like, a lubricating action is exhibitedby cohesion between the fluorine-containing hydrocarbon groups or thehydrocarbon groups Rf, which are hydrophobic groups. In a case where theRf group is the fluorine-containing hydrocarbon group, it is preferablethat a total carbon number is 6 to 50 and a total carbon number of afluorinated hydrocarbon group is 4 to 20. The Rf group may be, forexample, a saturated or unsaturated straight chain, branched chain, orcyclic hydrocarbon group, but may preferably be a saturated straightchain hydrocarbon group.

For example, in a case where the Rf group is the hydrocarbon group, itis preferable that the Rf group is a group represented by the followingGeneral Formula (4).

General Formula (4):

(where in General Formula (4), 1 is an integer selected from the rangeof 8 to 30, and more preferably 12 to 20).

Furthermore, in a case where the Rf group is the fluorine-containinghydrocarbon group, it is preferable that the Rf group is grouprepresented by following General Formula (5).

General Formula (5):

(where in General Formula (5), m and n are, respectively, integersindependently selected from each other within the following ranges: m: 2to 20, n: 3 to 18, and more preferably m: 4 to 13, n: 3 to 10).

The fluorinated hydrocarbon group may be concentrated at one position inthe molecule as described above or may be dispersed as in the followingGeneral Formula (6), and may be —CHF₂, —CHF—, or the like, as well as—CF₃ or —CF₂—.

General Formula (6):

(where in General Formulas (5) and (6), n1+n2=n and m1+m2=m).

The reason why the number of carbon atoms in General Formulas (4), (5),and (6) is limited as described above is because when the number (1 orthe sum of m and n) of carbon atoms constituting an alkyl group or afluorine-containing alkyl group is equal to or more than the above lowerlimit, a length becomes an appropriate length, so that the cohesionbetween the hydrophobic groups is effectively exhibited and friction andwear durability is improved. Furthermore, the reason is because when thenumber of carbon atoms is equal to or less than the above upper limit,solubility in a solvent of a lubricant including the carboxylicacid-based compound is kept good.

In particular, when the Rf group in General Formulas (1), (2) and (3)contains a fluorine atom, there is an effect in reducing a frictioncoefficient and improving traveling performance. However, it ispreferable to provide a hydrocarbon group between thefluorine-containing hydrocarbon group and the ester bond to separate thefluorine-containing hydrocarbon group and the ester bond from eachother, thereby securing stability of the ester bond and preventinghydrolysis.

Furthermore, the Rf group may have a fluoroalkyl ether group or aperfluoropolyether group.

An R group in General Formula (1) may be absent, but in a case where theR group in General Formula (1) is present, it is preferably ahydrocarbon chain having a relatively small number of carbon atoms.

Furthermore, the Rf group or R group contains one element or a pluralityof elements selected from the group including nitrogen, oxygen, sulfur,phosphorus, and halogen as constituent elements, and may further have ahydroxyl group, a carboxyl group, and a carbonyl group, an amino group,an ester bond, and the like, in addition to the functional groupdescribed above.

It is preferable that the carboxylic acid-based compound represented byGeneral Formula (1) is specifically at least one of the compounds shownbelow. In other words, it is preferable that the lubricant contains atleast one of the compounds shown below.

CF₃(CF₂)₇(CH₂)₁₀COOCH(COOH)CH₂COOH

CF₃(CF₂)₃(CH₂)₁₀COOCH(COOH)CH₂COOH

C₁₇H₃₅COOCH(COOH)CH₂COOH

CF₃(CF₂)₇(CH₂)₂OCOCH₂CH(C₁₈H₃₇)COOCH(COOH)CH₂COOH

CF₃(CF₂)₇COOCH(COOH)CH₂COOH

CHF₂(CF₂)₇COOCH(COOH)CH₂COOH

CF₃(CF₂)₇(CH₂)₂OCOCH₂CH(COOH)CH₂COOH

CF₃(CF₂)₇(CH₂)₆OCOCH₂CH(COOH)CH₂COOH

CF₃(CF₂)₇(CH₂)₁₁OCOCH₂CH(COOH)CH₂COOH

CF₃(CF₂)₃(CH₂)₆OCOCH₂CH(COOH)CH₂COOH

C₁₈H₃₇OCOCH₂CH(COOH)CH₂COOH

CF₃(CF₂)₇(CH₂)₄COOCH(COOH)CH₂COOH

CF₃(CF₂)₃(CH₂)₄COOCH(COOH)CH₂COOH

CF₃(CF₂)₃(CH₂)₇COOCH(COOH)CH₂COOH

CF₃(CF₂)₉(CH₂)₁₀COOCH(COOH)CH₂COOH

CF₃(CF₂)₇(CH₂)₁₂COOCH(COOH)CH₂COOH

CF₃(CF₂)₅(CH₂)₁₀COOCH(COOH)CH₂COOH

CF₃(CF₂)₇CH(C₉H₁₉)CH₂CH═CH(CH₂)₇COOCH(COOH)CH₂COOH

CF₃(CF₂)₇CH(C₆H₁₃)(CH₂)₇COOCH(COOH)CH₂COOH

CH₃(CH₂)₃(CH₂CH₂CH(CH₂CH₂(CF₂)₉CF₃))₂(CH₂)₇COOCH(COOH)CH₂COOH

The carboxylic acid-based compound represented by the General Formula(1) is soluble in a non-fluorinated solvent having a small load on anenvironment, and has an advantage that an operation such as coating,immersion, spraying, or the like, can be performed using ageneral-purpose solvent such as, for example, a hydrocarbon-basedsolvent, a ketone-based solvent, an alcohol-based solvent, anester-based solvent, and the like. Specifically, examples of thegeneral-purpose solvent can include hexane, heptane, octane, decane,dodecane, benzene, toluene, xylene, cyclohexane, methyl ethyl ketone,methyl isobutyl ketone, methanol, ethanol, isopropanol, diethyl ether,tetrahydrofuran, dioxane, cyclohexanone, and the like.

In a case where the protective layer 116 contains a carbon material,when the carboxylic acid-based compound is coated on the protectivelayer 116 as a lubricant, two carboxyl groups and at least one esterbond group, which are polar group parts of lubricant molecules, can beadsorbed on the protective layer 116 to form a particularly durablelubricating layer 117 by cohesion between hydrophobic groups.

Note that the lubricant is held not only on the surface of the magneticrecording medium 110 as the lubricating layer 117 as described above,but may also be contained and held in layers such as the magnetic layer115, the protective layer 116 and the like constituting the magneticrecording medium 110.

(Back Layer)

The description regarding the back layer 14 in the first embodiment isapplied to the back layer 118.

(3) Physical Properties and Structure

All of the descriptions regarding the physical properties and thestructure described in the above (3) of 2. are also applied to thesecond embodiment. For example, an average thickness t_(T) of themagnetic recording medium 110, a dimensional change amount Δw, adifference between a servo track width of an inner side of winding and aservo track width of an outer side of winding), a deviation amount ofthe servo track width, a temperature expansion coefficient α, and ahumidity expansion coefficient β, a Poisson's ratio ρ, an elastic limitvalue σ_(MD) in a longitudinal direction, a friction coefficient μbetween the magnetic surface and the back surface, and a surfaceroughness R_(ab) of the back layer 118 may be similar to those in thefirst embodiment. Therefore, a description of the physical propertiesand the structure of the magnetic recording medium of the secondembodiment is omitted.

(4) Configuration of Sputtering Apparatus

Hereinafter, an example of a configuration of a sputtering apparatus 120used for manufacturing the magnetic recording medium 110 will bedescribed with reference to FIG. 9. The sputtering apparatus 120 is acontinuous winding type sputtering used for forming the SUL 112, thefirst seed layer 113A, the second seed layer 113B, the first groundlayer 114A, the second ground layer 114B, and the magnetic layer 115,and includes a film forming chamber 121, a drum 122, which is a metalcan (rotary body), cathodes 123 a to 123 f, a supply reel 124, a windingreel 125, and a plurality of guide rollers 127 a to 127 c and 128 a to128 c, as shown in FIG. 9. The sputtering apparatus 120 is, for example,an apparatus using a DC (direct current) magnetron sputtering manner,but the sputtering manner is not limited thereto.

The film forming chamber 121 is connected to a vacuum pump (not shown)through an exhaust port 126, and the atmosphere in the film formingchamber 121 is set to a predetermined degree of vacuum by the vacuumpump. The drum 122 having a rotatable configuration, the supply reel124, and the winding reel 125 are arranged in the film forming chamber121. The plurality of guide rollers 127 a to 127 c for guidingconveyance of the base layer 111 between the supply reel 124 and thedrum 122 and the plurality of guide rollers 128 a to 128 c for guidingconveyance of the base layer 111 between the drum 122 and the windingreel 125 are provided in the film forming chamber 121. At the time ofsputtering, the base layer 111 unwound from the supply reel 124 is woundaround the winding reel 125 through the guide rollers 127 a to 127 c,the drum 122, and the guide rollers 128 a to 128 c. The drum 122 has acylindrical shape, and the long base layer 111 is conveyed along acircumferential surface of the cylindrical surface of the drum 122. Thedrum 122 is provided with a cooling mechanism (not shown), and is cooledto, for example, about −20° C. at the time of the sputtering. Aplurality of cathodes 123 a to 123 f is arranged in the film formingchamber 121 so as to face the circumferential surface of the drum 122Target are set on the cathodes 123 a to 123 f, respectively.Specifically, targets for forming the SUL 112, the first seed layer113A, the second seed layer 113B, the first ground layer 114A, thesecond ground layer 114B, and the magnetic layer 115 are set on thecathodes 123 a, 123 b, 123 c, 123 d, 123 e, and 123 f, respectively. Aplurality of types of films, that is, the SUL 112, the first seed layer113A, the second seed layer 113B, the first ground layer 114A, thesecond ground layer 114B, and the magnetic layer 115 are simultaneouslyformed by these cathodes 123 a to 123 f.

In the sputtering apparatus 120 having the configuration describedabove, the SUL 112, the first seed layer 113A, the second seed layer113B, the first ground layer 114A, the second ground layer 114B, and themagnetic layer 115 are continuously formed by a RolltoRoll method.

(5) Method of Manufacturing Magnetic Recording Medium

The magnetic recording medium 110 can be manufactured, for example, asfollows.

First, the SUL 112, the first seed layer 113A, the second seed layer113B, the first ground layer 114A, the second ground layer 114B, and themagnetic layer 115 are sequentially formed on a surface of the baselayer 111 using the sputtering apparatus 120 shown in FIG. 9.Specifically, the films are formed as follows. First, the film formingchamber 121 is evacuated to a predetermined pressure. Thereafter, thetargets set on the cathodes 123 a to 123 f are sputtered while a processgas such as an Ar gas or the like is introduced into the film formingchamber 121 Therefore, the SUL 112, the first seed layer 113A, thesecond seed layer 113B, the first ground layer 114A, the second groundlayer 114B, and the magnetic layer 115 are sequentially formed on thesurface of the traveling base layer 111.

The atmosphere of the film forming chamber 121 at the time of thesputtering is set to, for example, about 1×10⁻⁵ Pa to 5×10⁻⁵ Pa. Filmthicknesses and characteristics of the SUL 112, the first seed layer113A, the second seed layer 113B, the first ground layer 114A, thesecond ground layer 114B, and the magnetic layer 115 can be controlledby adjusting a tape line speed at which the base layer 111 is wound, apressure (sputtering gas pressure) of the process gas such as the Ar gasor the like introduced at the time of the sputtering, supplied power,and the like.

Next, the protective layer 116 is formed on the magnetic layer 115. As amethod of forming the protective layer 116, for example, a chemicalvapor deposition (CVD) method or a physical vapor deposition (PVD)method can be used.

Next, a binder, inorganic particles, a lubricant, and the like arekneaded and dispersed in a solvent to prepare a coating material forforming a back layer. Next, the back layer 118 is formed on the backsurface of the base layer 111 by applying the coating material forforming a back layer on the back surface of the base layer 111 and thendrying the coating material.

Next, for example, the lubricant is coated on the protective layer 116to form the lubricating layer 117. As a method of coating the lubricant,for example, various coating methods such as gravure coating, dipcoating and the like can be used. Next, the magnetic recording medium110 is cut into a predetermined width, as necessary. Thus, the magneticrecording medium 110 shown in FIG. 8 is obtained.

(6) Effect

In the magnetic recording cartridge according to the second embodiment,a recording capacity can be high and a change in the width of themagnetic recording medium 110 can be suppressed by adjusting tension ina longitudinal direction of the magnetic recording medium 110 by therecording and reproducing apparatus, similar to the first embodiment.

Moreover, the magnetic recording medium 110 is accommodated in a stateof being wound around a reel and (servo track width inside the magneticrecording medium)−(servo track width outside the magnetic recordingmedium)>0 is satisfied. As a result, the occurrence of wrinkles on theinner side of winding in the cartridge may be suppressed.

As described above, the magnetic recording cartridge according to thesecond embodiment has high recording capacity per cartridge, is suitablefor use in a recording and reproducing apparatus which adjusts tensionin the longitudinal direction of the magnetic recording medium, andsuppresses the occurrence of wrinkles that may occur with the tensionadjustment.

(7) Modification

The magnetic recording medium 110 may further include a ground layerbetween the base layer 111 and the SUL 112. Since the SUL 112 has theamorphous state, the SUL 112 does not play a role of promoting epitaxialgrowth of a layer formed on the SUL 112, but is desired not to disturbthe crystal alignment of the first and second ground layers 114A and114B formed on the SUL 112. For this purpose, it is preferable that thesoft magnetic material has a fine structure that does not form a column,but in a case where an influence of the release of a gas such asmoisture or the like from the base layer 111 is large, the soft magneticmaterial may be coarsened to disturb the crystal alignment of the firstand second ground layers 114A and 114B formed on the SUL 112. In orderto suppress the influence of the release of the gas such as moisture orthe like from the base layer 111, it is preferable that the ground layercontaining an alloy containing Ti and Cr and an having amorphous stateis provided between the base layer 111 and the SUL 112, as describedabove. As a specific configuration of the ground layer, a configurationsimilar to that of the first seed layer 113A of the second embodimentcan be adopted.

The magnetic recording medium 110 may not include at least one of thesecond seed layer 113B or the second ground layer 114B. However, it ismore preferable that the magnetic recording medium 110 includes both ofthe second seed layer 113B and the second base layer 114B, in terms ofimprovement a SNR.

The magnetic recording medium 110 may include an antiparallel coupledSUL (APC-SUL) instead of the single-layer SUL.

(8) Other Examples of Magnetic Recording Media

(Configuration of Magnetic Recording Medium)

The magnetic recording cartridge 1 may include a magnetic recordingmedium 130 as described later, instead of the magnetic recording medium110. The magnetic recording medium 130 includes a base layer 111, a SUL112, a seed layer 131, a first ground layer 132A, a second ground layer132B, and a magnetic layer 115, as shown in FIG. 10. Note that regardinga description of the magnetic recording medium 130, the same componentsas those of the magnetic recording medium 110 will be denoted by thesame reference numerals, and a description thereof will be omitted.

The SUL 112, the seed layer 131, and the first and second ground layers132A and 132B are provided between one main surface of the base layer111 and the magnetic layer 115, and the SUL 112, the seed layer 131, thefirst ground layer 132A, and the second ground layer 132B aresequentially stacked from the base layer 111 toward the magnetic layer115.

(Seed Layer)

The seed layer 131 contains Cr, Ni, and Fe, and has a face-centeredcubic lattice (fcc) structure, and a (111) plane of the face-centeredcubic lattice structure is preferentially aligned so as to be parallelwith a surface of the base layer 111. Here, the preferential alignmentmeans a state in which a diffraction peak intensity from the (111) planeof the face-centered cubic lattice structure is larger than diffractionpeaks from other crystal planes in a θ-2θ scan of an X-ray diffractionmethod or a state in which only the diffraction peak intensity from the(111) plane of the face-centered cubic lattice structure is observed inthe θ-2θ scan of the X-ray diffraction method.

An intensity ratio of X-ray diffraction of the seed layer 131 ispreferably 60 cps/nm or more, more preferably 70 cps/nm or more, andstill more preferably 80 cps/nm or more, in terms of improvement of theSNR. Here, the intensity ratio of the X-ray diffraction of the seedlayer 131 is a value (I/D)(cps/nm)) obtained by dividing an intensityI(cps) of the X-ray diffraction of the seed layer 131 by an averagethickness D (nm) of the seed layer 131.

It is preferable that Cr, Ni, and Fe contained in the seed layer 131have an average composition represented by the following Formula (2).Cr_(X)(Ni_(Y)Fe_(100-Y))_(100-X)  (2)

(where in Formula (2), X is in the range in which 10≤X≤45 is satisfied,Y is in the range in which 60≤Y≤90 is satisfied). When X is in the aboverange, (111) alignment of a face-centered cubic lattice structure of Cr,Ni, and Fe is improved, so that a better SNR can be obtained. Similarly,when Y is in the above range, the (111) alignment of the face-centeredcubic lattice structure of Cr, Ni, and Fe is improved, so that a betterSNR can be obtained.

It is preferable that the average thickness of the seed layer 131 is 5nm or more to 40 nm or less. By setting the average thickness of theseed layer 131 to be in this range, the (111) alignment of theface-centered cubic lattice structure of Cr, Ni, and Fe is improved, sothat a better SNR can be obtained. Note that the average thickness ofthe seed layer 131 is obtained in a manner similar to that of themagnetic layer 13 in the first embodiment. However, a magnification of aTEM image is appropriately adjusted according to the thickness of theseed layer 131.

(First and Second Ground Layers)

The first ground layer 132A contains Co and O having a face-centeredcubic lattice structure, and has a column (columnar crystal) structure.In the first ground layer 132A containing Co and O, substantially aneffect (function) substantially similar to that of the second groundlayer 132B containing Ru is obtained. A concentration ratio of anaverage atomic concentration of O to an average atomic concentration ofCo ((average atomic concentration of O)/(average atomic concentration ofCo)) is 1 or more. When the concentration ratio is 1 or more, the effectof providing the first base layer 132A is improved, so that a better SNRcan be obtained.

It is preferable that the column structure is inclined in terms ofimprovement of the SNR. It is preferable that a direction of theinclination is a longitudinal direction of the long-shaped magneticrecording medium 130. The reason why it is preferable that the directionof the inclination is the longitudinal direction is as follows. Themagnetic recording medium 130 is a so-called magnetic recording mediumfor linear recording, and a recording track is parallel with thelongitudinal direction of the magnetic recording medium 130.Furthermore, the magnetic recording medium 130 is also a so-calledperpendicular magnetic recording medium, and it is preferable that acrystal alignment axis of the magnetic layer 115 is perpendicular interms of recording characteristics, but an inclination may be generatedin the crystal alignment axis of the magnetic layer 115 due to aninfluence of an inclination of the column structure of the first groundlayer 132A. In the magnetic recording medium 130 for linear recording,in a relationship with the head magnetic field at the time of recording,the influence of the inclination of the crystal alignment axis on therecording characteristics can be reduced in a configuration in which thecrystal alignment axis of the magnetic layer 115 is inclined in thelongitudinal direction of the magnetic recording medium 130 as comparedwith a configuration in which the crystal alignment axis of the magneticlayer 115 is inclined in the width direction of the magnetic recordingmedium 130. In order to incline the crystal alignment axis of themagnetic layer 115 in the longitudinal direction of the magneticrecording medium 130, it is preferable that the inclination direction ofthe column structure of the first ground layer 132A is the longitudinaldirection of the magnetic recording medium 130 as described above.

It is preferable that the inclination angle of the column structure islarger than 0° and is 60° or less. In the range in which the inclinationangle is large than 0° and is 60° or less, a change in a tip shape ofthe column contained in the first ground layer 132A is large, so thatthe tip shape becomes substantially a triangular shape. Therefore, aneffect of the granular structure tends to be improved, noise tends to bereduced, and the SNR tends to be improved. On the other hand, when theinclination angle exceeds 60°, the change in the tip shape of the columncontained in the first foundation layer 132A is small, so that it isdifficult for the tip shape to become substantially a triangular shape.Therefore, a noise reduction effect tends to be degraded.

An average particle diameter of the column structure is 3 nm or more to13 nm or less. when the average particle size is less than 3 nm, theaverage particle size of the column structure included in the magneticlayer 115 is reduced, and thus, there is a possibility that an abilityto hold a record with a current magnetic material will be deteriorated.On the other hand, when the average particle size is 13 nm or less, thenoise is suppressed, so that a better SNR can be obtained.

An average thickness of the first ground layer 132A is preferably 10 nmor more to 150 nm or less. When the average thickness of the firstground layer 132A is 10 nm or more, (111) alignment of the face-centeredcubic lattice structure of the first ground layer 132A is improved, sothat a better SNR can be obtained. On the other hand, when the averagethickness of the first ground layer 132A is 150 nm or less, an increasein a particle diameter of the column can be suppressed. Therefore, thenoise is suppressed, so that a better SNR can be obtained. Note that theaverage thickness of the first ground layer 132A is obtained in a mannersimilar to the magnetic layer 13 in the first embodiment. However, amagnification of a TEM image is appropriately adjusted according to thethickness of the first ground layer 132A.

It is preferable that the second ground layer 132B has a crystalstructure similar to that of the magnetic layer 115. In a case where themagnetic layer 115 contains a Co-based alloy, the second ground layer132B contains a material having a hexagonal closest-packed (hcp)structure similar to that of the Co-based alloy, and it is preferablethat a c-axis of the hcp structure is aligned in a direction (that is, afilm thickness direction) perpendicular to a film surface. The reason isbecause alignment of the magnetic layer 115 can be improved and matchingin a lattice constant between the second ground layer 132B and themagnetic layer 115 can be made relatively good. As the material havingthe hexagonal closest-packed structure, it is preferable to use amaterial containing Ru, and specifically, it is preferable to use Rualone or use a Ru alloy. Examples of the Ru alloy can include an Rualloy oxide such as Ru—SiO₂, Ru—TiO₂, Ru—ZrO₂, or the like.

An average thickness of the second ground layer 132B may be thinner thanthat of a ground layer (for example, a ground layer containing Ru) in ageneral magnetic recording medium, and can be, for example, 1 nm or moreto 5 nm or less. Since the seed layer 131 and the first ground layer132A having the configurations described above are provided under thesecond ground layer 132B, even though the average thickness of thesecond ground layer 132B is thin as described above, a good SNR isobtained. Note that the average thickness of the second ground layer132B is obtained in a manner similar to the magnetic layer 13 in thefirst embodiment. However, a magnification of a TEM image isappropriately adjusted according to the thickness of the second groundlayer 132B.

(Effect)

In the magnetic recording cartridge according to the second embodiment,even in a case of using the magnetic recording medium 130 instead of themagnetic recording medium 110, a recording capacity can be high and achange in the width of the magnetic recording medium 130 can besuppressed by adjusting tension in a longitudinal direction of themagnetic recording medium 130 by the recording and reproducingapparatus, similar to the first embodiment.

The magnetic recording medium 130 includes the seed layer 131 and thefirst ground layer 132A between the base layer 111 and the second groundlayer 132B. The seed layer 131 contains Cr, Ni, and Fe, and

has a face-centered cubic lattice structure, and a (111) plane of theface-centered cubic structure is preferentially aligned so as to beparallel with a surface of the base layer 111. The first ground layer132A has a column structure in which it contains Co and O, a ratio of anaverage atomic concentration of O to an average atomic concentration ofCo is 1 or more, and an average particle diameter is 3 nm or more to 13nm or less. Therefore, it is possible to realize the magnetic layer 115having a good crystal alignment and a high coercive force without usingRu, which is an expensive material, as thin as possible by reducing thethickness of the second ground layer 132B.

Ru contained in the second ground layer 132B has the same hexagonalclosest-packed lattice structure as that of Co, which is a maincomponent of the magnetic layer 115. Therefore, Ru has an effect ofimproving the crystal alignment of the magnetic layer 115 and promotinga granular property. Furthermore, in order to further improve thecrystal alignment of Ru contained in the second ground layer 132B, thefirst ground layer 132A and the seed layer 131 are provided under thesecond ground layer 132B. In the magnetic recording medium 130, aneffect (function) substantially similar to that of the second groundlayer 132B containing Ru is realized by the first ground layer 132Acontaining cheap CoO having the face-centered cubic lattice structure.Therefore, the thickness of the second ground layer 132B can be reduced.Furthermore, in order to improve the crystal alignment of the firstground layer 132A, the seed layer 131 containing Cr, Ni, and Fe isprovided.

4. EXAMPLE

Hereinafter, the present technology will be specifically described byExamples, but the present technology is not limited to only theseExamples.

In the following Examples and Comparative Examples, an average thicknesst_(T) of a magnetic tape, a dimensional change amount Δw in a widthdirection of the magnetic tape to a tension change in a longitudinaldirection of the magnetic tape, a temperature expansion coefficient α ofthe magnetic tape, a humidity expansion coefficient β of the magnetictape, a Poisson's ratio ρ of the magnetic tape, an elastic limit valueα_(MD) in the longitudinal direction of the magnetic tape, an averagethickness t_(m) of a magnetic layer, a squareness ratio S2, an averagethickness t_(b) of a back layer, a surface roughness R_(ab) of the backlayer, an interlayer friction coefficient μ between a magnetic surfaceand a back surface, an amount of deviation of a servo track width of aninner side of winding (an amount of a deviation with a reproducing servoread head width) T_(in)W, an amount of deviation of a servo track widthof an outer side of the winding (an amount of a deviation with areproducing servo read head width) T_(out)W, and a difference in a servotrack width between the inner side and the outer side of the winding(T_(in)W−T_(out)W) are values obtained by a measurement method describedin the first embodiment. However, as described later, in Example 11, aspeed Vat the time of measuring an elastic limit value σ_(MD) in alongitudinal direction was set to a value different from the measurementmethod described in the first embodiment.

Example 1

(Process of Preparing Magnetic Layer-Forming Coating Material)

A magnetic layer-forming coating material was prepared as follows.First, a first composition of the following mixture was kneaded with anextruder. Next, the kneaded first composition and a second compositionof the following mixture were added to a stirring tank equipped with adisperser and preliminary mixing was carried out. Subsequently, sandmill mixing was performed again and subjected to filtering to prepare amagnetic layer-forming coating material.

(First Composition)

Powder of ε iron oxide nanoparticles (ε-Fe₂O₃ crystal particles): 100parts by mass

Vinyl chloride resin (30% by mass of a cyclohexanone solution): 10 partsby mass (containing a polymerization degree of 300, Mn=10000, OSO₃K=0.07mmol/g as a polar group, and secondary OH=0.3 mmol/g)

Aluminum oxide powder: 5 parts by mass

(α-Al₂O₃, average particle size 0.2 μm)

Carbon black: 2 parts by mass

(Manufactured by TOKAI CARBON CO., LTD, trade name: SEAST TA)

(Second Composition)

Vinyl chloride resin: 1.1 parts by mass

(Resin solution: 30% by mass of resin, 70% by mass of cyclohexanone)

n-Butyl stearate: 2 parts by mass

Methyl ethyl ketone: 121.3 parts by mass

Toluene: 121.3 parts by mass

Cyclohexanone: 60.7 parts by mass

Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L,manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass ofmyristic acid were added as a curing agent to the magnetic layer-formingcoating material prepared as described above.

(Process of Preparing Ground Layer-Forming Coating Material)

A ground layer-forming coating material was prepared as follows. First,a third composition of the following mixture was kneaded by an extruder.Next, the kneaded third composition and a fourth composition of thefollowing mixture were added to a stirring tank equipped with a disperand preliminary mixing was carried out. Subsequently, sand mill mixingwas further performed and the mixture was subjected to filtering toprepare a ground layer-forming coating material.

(Third Composition)

Needle-like iron oxide powder: 100 parts by mass

(α-Fe₂O₃, average major axis length 0.15 μm)

Vinyl chloride resin: 55.6 parts by mass

(Resin solution: 30% by mass of resin, 70% by mass of cyclohexanone)

Carbon black: 10 parts by mass

(Average particle size 20 nm)

(Fourth Composition)

Polyurethane resin UR8200 (manufactured by TOYO BOSEKI): 18.5 parts bymass

n-Butyl stearate: 2 parts by mass

Methyl ethyl ketone: 108.2 parts by mass

Toluene: 108.2 parts by mass

Cyclohexanone: 18.5 parts by mass

Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L,manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass ofmyristic acid were added as a curing agent to the ground layer-formingcoating material prepared as described above.

(Process of Preparing Back Layer-Forming Coating Material)

A back layer-forming coating material was prepared as follows. Thefollowing raw materials were mixed in a stirring tank equipped with adisper and subjected to filtering to prepare a back layer-formingcoating material.

Carbon black (manufactured by Asahi Carbon Co., Ltd., trade name: #80):100 parts by mass

Polyester polyurethane: 100 parts by mass

(Nippon Polyurethane Co., Ltd., trade name: N-2304)

Methyl ethyl ketone: 500 parts by mass

Toluene: 400 parts by mass

Cyclohexanone: 100 parts by mass

(Film Formation Process)

Using the coating material prepared as described above, a ground layerhaving an average thickness of 1.0 μm and a magnetic layer having anaverage thickness tm of 90 nm were formed on a long polyethylenenaphthalate film (hereinafter referred to as “PEN film”) which is anonmagnetic support in the following manner. First, the groundlayer-forming coating material was applied to the film and dried to forma ground layer on the film. Next, a magnetic layer-forming coatingmaterial was applied to the ground layer and dried to form a magneticlayer on the ground layer. Note that, when the magnetic layer-formingcoating material was dried, the magnetic powder was magnetically alignedin a thickness direction of the film by a solenoid coil. Furthermore,the squareness ratio S2 in the thickness direction (vertical direction)of the magnetic tape was set to 65% by adjusting an application time ofthe magnetic field to the magnetic layer-forming coating material.

Subsequently, a back layer having an average thickness t_(b) of 0.6 μmwas applied to the film, on which the ground layer and the magneticlayer were formed, and dried. Then, the film, on which the ground layer,the magnetic layer, and the back layer were formed, was subjected to acuring treatment. Subsequently, calendering was performed to smooth thesurface of the magnetic layer. Here, conditions (temperature) forcalendering were adjusted so that an interlayer friction coefficient μof a magnetic surface and a back surface was about 0.5 and re-curing wassubsequently performed to obtain a magnetic tape having an averagethickness t_(T) of 5.5 μm.

(Cutting Process)

The magnetic tape obtained as described above was cut into a ½ inch(12.65 mm) width and wound around a core to obtain a pancake.

The magnetic tape obtained as described above had the characteristicsshown in Table 1. For example, a dimensional change amount Δw of themagnetic tape was 707 ppm/N.

The ½ inch-wide magnetic tape was wound around a reel prepared in thecartridge case to obtain a magnetic recording cartridge. A servo signalwas recorded on the magnetic tape. The servo signal includes a series ofinverted V-shaped magnetic patterns, and the magnetic patterns arepre-recorded in parallel in the longitudinal direction at two or morelines at known intervals (hereinafter referred to as “standard servotrack width”).

Example 2

A magnetic tape was obtained in the same manner as in Example 1 exceptthat the thickness of the PEN film was made thinner than in Example 1 sothat the dimensional change amount Δw was 750 ppm/N. The averagethickness t_(T) of the magnetic tape was 5 μm. As in Example 1, amagnetic recording cartridge was manufactured using the magnetic tapeand a servo signal was then recorded on the magnetic tape.

Example 3

A magnetic tape was obtained in the same manner as in Example 1 exceptthat the thickness of the PEN film was thinner than Example 1 and theaverage thickness of the back layer and the ground layer was thinner sothat the dimensional change amount Δw was 800 ppm/N. The averagethickness t_(T) of the magnetic tape was 4.5 μm. As in Example 1, amagnetic recording cartridge was manufactured using the magnetic tapeand a servo signal was then recorded on the magnetic tape.

Example 4

A magnetic tape was obtained in the same manner as in Example 1 exceptthat the thickness of the PEN film was thinner than Example 1, theaverage thickness of the back layer and the ground layer was thinner,and the curing treatment conditions of the film on which the groundlayer, the magnetic layer, and the back layer were formed were adjustedso that the dimensional change amount Δw was 800 ppm/N. As in Example 1,a magnetic recording cartridge was manufactured using the magnetic tapeand a servo signal was then recorded on the magnetic tape.

Example 5

A magnetic tape was obtained in the same manner as in Example 4 exceptthat the composition of the ground layer-forming coating material waschanged so that the thermal expansion coefficient α was 8.0 ppm/° C. Asin Example 1, a magnetic recording cartridge was manufactured using themagnetic tape and a servo signal was then recorded on the magnetic tape.

Example 6

A magnetic tape was obtained in the same manner as in Example 4 exceptthat a thin barrier layer was formed on one side of the PEN film so thatthe humidity expansion coefficient β was 3.0 ppm/% RH. As in Example 1,a magnetic recording cartridge was manufactured using the magnetic tapeand a servo signal was then recorded on the magnetic tape.

Example 7

A magnetic tape was obtained in the same manner as in Example 4 exceptthat longitudinal and transverse stretching strengths of the base filmwere changed so that the Poisson's ratio ρ was 0.31. As in Example 1, amagnetic recording cartridge was manufactured using the magnetic tapeand a servo signal was then recorded on the magnetic tape.

Example 8

A magnetic tape was obtained in the same manner as in Example 4 exceptthat the longitudinal and transverse stretching strengths of the basefilm were changed so that the Poisson's ratio ρ was 0.35. As in Example1, a magnetic recording cartridge was manufactured using the magnetictape and a servo signal was then recorded on the magnetic tape.

Example 9

A magnetic tape was obtained in the same manner as in Example 7 exceptthat the curing conditions of the film on which the ground layer, themagnetic layer, and the back layer were formed were adjusted so that theelastic limit value σ_(MD) in the longitudinal direction was 0.8 N. Asin Example 1, a magnetic recording cartridge was manufactured using themagnetic tape and a servo signal was then recorded on the magnetic tape.

Example 10

A magnetic tape was obtained in the same manner as in Example 7 exceptthat the curing conditions and re-curing conditions of the film on whichthe ground layer, the magnetic layer, and back layer were formed wereadjusted so that the elastic limit value σ_(MD) in the longitudinaldirection was 3.5 N. As in Example 1, a magnetic recording cartridge wasmanufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Example 11

A magnetic tape was obtained in a manner similar to that of Example 9.Then, the elastic limit value σ_(MD) of the obtained magnetic tape wasmeasured by changing the speed V when measuring the elastic limit valueσ_(MD) in the longitudinal direction to 5 mm/min. As a result, theelastic limit value σ_(MD) in the longitudinal direction was 0.8,without any change as compared with the elastic limit value σ_(MD) inthe longitudinal direction at a speed V of 0.5 mm/min (Example 9). As inExample 1, a magnetic recording cartridge was manufactured using themagnetic tape and a servo signal was then recorded on the magnetic tape.

Example 12

A magnetic tape was obtained in the same manner as in Example 7 exceptthat a coating thickness of the magnetic layer-forming coating materialwas changed so that the average thickness t_(m) of the magnetic layerwas 40 nm. As in Example 1, a magnetic recording cartridge wasmanufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Example 13 Film Formation Process of SUL

First, a CoZrNb layer (SUL) having an average thickness of 10 nm wasformed on a surface of a long polymer film as a nonmagnetic supportunder the following film formation conditions. Note that a PEN film wasused as the polymer film.

Film formation method: DC magnetron sputtering method

Target: CoZrNb target

Gas type: Ar

Gas pressure: 0.1 Pa

(Process of Forming First Seed Layer)

Next, a TiCr layer (first seed layer) having an average thickness of 5nm was formed on the CoZrNb layer under the following film formationconditions.

Sputtering method: DC magnetron sputtering method

Target: TiCr target

Achieved vacuum: 5×10⁻⁵ Pa

Gas type: Ar

Gas pressure: 0.5 Pa

(Process of Forming Second Seed Layer)

Next, a NiW layer (second seed layer) having an average thickness of 10nm was formed on the TiCr layer under the following film formationconditions.

Sputtering method: DC magnetron sputtering method

Target: NiW target

Achieved vacuum: 5×10⁻⁵ Pa

Gas type: Ar

Gas pressure: 0.5 Pa

(Process of Forming First Ground Layer)

Next, a Ru layer (first ground layer) having an average thickness of 10nm was formed on the NiW layer under the following film formationconditions.

Sputtering method: DC magnetron sputtering method

Target: Ru target

Gas type: Ar

Gas pressure: 0.5 Pa

(Process of Forming Second Ground Layer)

Next, a Ru layer (second ground layer) having an average thickness of 20nm was formed on the Ru layer under the following film formationconditions.

Sputtering method: DC magnetron sputtering method

Target: Ru target

Gas type: Ar

Gas pressure: 1.5 Pa

(Process of Forming Magnetic Layer)

Next, a (CoCrPt)—(SiO₂) layer (magnetic layer) having an averagethickness of 9 nm was formed on the Ru layer under the following filmformation conditions.

Film formation method: DC magnetron sputtering method

Target: (CoCrPt)—(SiO₂)target

Gas type: Ar

Gas pressure: 1.5 Pa

(Process of Forming Protective Layer)

Next, a carbon layer (protective layer) having an average thickness of 5nm was formed on the magnetic layer under the following film formationconditions.

Film formation method: DC magnetron sputtering method

Target: carbon target

Gas type: Ar

Gas pressure: 1.0 Pa

(Process of Forming Lubricating Layer)

Next, a lubricant was applied to the protective layer to form alubricating layer.

(Process of Forming Back Layer)

Next, a back layer-forming coating material was applied to a surfaceopposite to the magnetic layer and dried to form a back layer having anaverage thickness t_(b) of 0.3 μm. As a result, a magnetic tape havingan average thickness t_(T) of 4.0 μm was obtained.

(Cutting Process)

The magnetic tape obtained as described above was cut into a ½ inch(12.65 mm) width.

The magnetic tape obtained as described above had the characteristicsshown in Table 1. For example, the dimensional change amount Δw of themagnetic tape was 800 ppm/N. As in Example 1, a magnetic recordingcartridge was manufactured using the magnetic tape and a servo signalwas then recorded on the magnetic tape.

Example 14

A magnetic tape was obtained in the same manner as in Example 7 exceptthat the thickness of the back layer was changed to 0.2 μm. An averagethickness of the magnetic tape was 4.4 μm. As in Example 1, a magneticrecording cartridge was manufactured using the magnetic tape and a servosignal was then recorded on the magnetic tape.

Example 15

A magnetic tape was obtained in the same manner as in Example 7 exceptthat the composition of the back layer-forming coating material waschanged so that the surface roughness R_(ab) of the back layer was 3 nm.As in Example 1, a magnetic recording cartridge was manufactured usingthe magnetic tape and a servo signal was then recorded on the magnetictape.

Example 16

A magnetic tape was obtained in the same manner as in Example 7 exceptthat the conditions (temperature) of calendering were adjusted so thatthe friction coefficient μ was 0.20. As in Example 1, a magneticrecording cartridge was manufactured using the magnetic tape and a servosignal was then recorded on the magnetic tape.

Example 17

A magnetic tape was obtained in the same manner as in Example 7 exceptthat the composition of the back layer-forming coating material waschanged so that the surface roughness R_(ab) of the back layer was 3 nmand the conditions (temperature) of the calendering were adjusted sothat the friction coefficient μ was 0.80. As in Example 1, a magneticrecording cartridge was manufactured using the magnetic tape and a servosignal was then recorded on the magnetic tape.

Example 18

A magnetic tape was obtained in the same manner as in Example 7, exceptthat the coating thickness of the magnetic layer-forming coatingmaterial was changed so that the average thickness t_(m) of the magneticlayer was 110 nm. As in Example 1, a magnetic recording cartridge wasmanufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Example 19

A magnetic tape was obtained in the same manner as in Example 7, exceptthat the composition of the back layer-forming coating material waschanged so that the surface roughness R_(ab) of the back layer was 7 nm.As in Example 1, a magnetic recording cartridge was manufactured usingthe magnetic tape and a servo signal was then recorded on the magnetictape.

Example 20

A magnetic tape was obtained in the same manner as in Example 7, exceptthat the conditions (temperature) for calendering were adjusted so thatthe friction coefficient μ was 0.18. As in Example 1, a magneticrecording cartridge was manufactured using the magnetic tape and a servosignal was then recorded on the magnetic tape.

Example 21

A magnetic tape was obtained in the same manner as in Example 7, exceptthat the conditions (temperature) for calendering were adjusted so thatthe friction coefficient μ was 0.82. As in Example 1, a magneticrecording cartridge was manufactured using the magnetic tape and a servosignal was then recorded on the magnetic tape.

Example 22

A magnetic tape was obtained in the same manner as in Example 7, exceptthat the squareness ratio S2 in the thickness direction (verticaldirection) of the magnetic tape was set to 73% by adjusting theapplication time of the magnetic field to the magnetic layer-formingcoating material. As in Example 1, a magnetic recording cartridge wasmanufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Example 23

A magnetic tape was obtained in the same manner as in Example 7, exceptthat the squareness ratio S2 in the thickness direction (verticaldirection) of the magnetic tape was set to 80% by adjusting theapplication time of the magnetic field to the magnetic layer-formingcoating material. As in Example 1, a magnetic recording cartridge wasmanufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Example 24

A magnetic tape was obtained in the same manner as in Example 7 exceptthat the curing conditions and re-curing conditions of the film on whichthe ground layer, the magnetic layer, and the back layer were formedwere adjusted so that the elastic limit value σ_(MD) in the longitudinaldirection was 5 N. As in Example 1, a magnetic recording cartridge wasmanufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Example 25

A magnetic tape was obtained in the same manner as in Example 7, exceptthat barium ferrite (BaFe₁₂O₁₉) nanoparticles were used instead of εiron oxide nanoparticles. As in Example 1, a magnetic recordingcartridge was manufactured using the magnetic tape and a servo signalwas then recorded on the magnetic tape.

Example 26

A magnetic tape was manufactured in the same manner as in Example 1except that the servo signal was recorded while running at a lowtension. As in Example 1, a magnetic recording cartridge wasmanufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Comparative Example 1

A magnetic tape was obtained in the same manner as in Example 1 exceptthat the stretching treatment of the PEN film was changed so that thedimensional change amount Δw was 650[ppm/N] and the winding tension inthe coating process was increased. As in Example 1, a magnetic recordingcartridge was manufactured using the magnetic tape and a servo signalwas then recorded on the magnetic tape.

Comparative Example 2

A magnetic tape was manufactured in the same manner as Example 2, exceptthat a thicker base film was used and the servo signal was recorded,while adjusting tension. As in Example 1, a magnetic recording cartridgewas manufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Comparative Example 3

A magnetic tape was manufactured in the same manner as Example 2, exceptthat a thicker base film was used and the servo signal was recorded,while adjusting tension. As in Example 1, a magnetic recording cartridgewas manufactured using the magnetic tape and a servo signal was thenrecorded on the magnetic tape.

Comparative Example 4

A magnetic tape was obtained in the same manner as in Example 7 exceptthat vertical alignment was not performed. As in Example 1, a magneticrecording cartridge was manufactured using the magnetic tape and a servosignal was then recorded on the magnetic tape.

(Determination of Change Amount of Tape Width)

As described above, on the magnetic tape included in the magneticrecording cartridge, two or more rows of inverted V-shaped magneticpatterns are previously recorded in parallel in the longitudinaldirection at a known interval (“standard servo track width”). Themagnetic recording tape in each magnetic recording cartridge wasreciprocated in the recording and reproducing apparatus. Then, at thetime of reciprocation running, two or more rows of the above-mentionedinverted V-shaped magnetic pattern rows were simultaneously reproduced,and the interval between the magnetic pattern rows during running wascontinuously measured from a shape of a reproduction waveform of eachrow. Note that at the time of running, rotational driving of the spindledriving device and the reel driving device was controlled on the basisof the measured interval information of the magnetic pattern row toautomatically adjust tension in the longitudinal direction of themagnetic tape so that the interval between the magnetic pattern rowsbecomes a prescribed width or substantially a prescribed width. A simpleaverage of all measured values for one reciprocation running of theinterval between the magnetic pattern rows is determined as a “measuredinterval between magnetic pattern rows”, and a difference between thisand the “standard servo track width” is a “change in tape width”.

Furthermore, the reciprocation running by the recording and reproducingapparatus was performed in a constant temperature and humidity chamber.A speed of the reciprocation was 5 m/sec. A temperature and humidityduring the reciprocation running were gradually and repeatedly changedaccording to a predetermined environmental change program in atemperature range of 10° C. to 45° C. and the relative humidity range of10% to 80%, independent of the reciprocation running described above(for example, the predetermined environmental change program may be, forexample, that 10° C. and 10%→29° C. and 80%→10° C. and 10% are repeatedtwice, in this case, the temperature and humidity are changed from 10°C. and 10% to 29° C. and 80% in two hours and from 29° C. and 80% to 10°C. and 10% in two hours).

This evaluation was repeated until the “predetermined environmentalchange program” was finished. After the evaluation, an average value(simple average) was calculated using all the absolute values of each ofthe “change in tape width” obtained at each reciprocation, and the valuewas determined as an “effective change amount of tape width” of thetape. A determination was made on each tape according to deviation (thesmaller the better) from an ideal of the “effective change amount oftape width”, and eight-stage determination values were respectivelygiven. Note that evaluation “8” indicated the most desirabledetermination result and evaluation “1” indicated the most undesirabledetermination result. The magnetic tape has certain evaluation of the 8stages, and the following states are observed when the magnetic taperuns.

8: No abnormality occurred

7: A slight increase in error speed is observed when running

6: A serious increase in error speed is observed when running

5: During running, the magnetic tape may not read a servo signal andslight (one or two) reloading is performed

4: During running, the magnetic tape may not read a servo signal andmedium (up to 10 times) reloading is performed

3: During running, the magnetic tape may not read a servo signal andheavy (more than 10 times) reloading is performed

2: The magnetic tape may not read servo and occasionally stops due to asystem error

1: The magnetic tape may not read servo and immediately stops due to asystem error

(Evaluation of Electromagnetic Conversion Characteristic)

First, a reproduction signal of the magnetic tape was acquired using aloop tester (manufactured by Microphysics). The conditions for acquiringthe reproduction signal are described below.

Head: GMR

Headspeed: 2 m/s

Signal: single recording frequency (10 MHz)

Recording current: Optimal recording current

Next, the reproduction signal was adopted by a spectrum analyzer at aspan (SPAN) of 0 to 20 MHz (resolution band width=100 kHz, VBW=30 kHz).Next, a peak of the adopted spectrum was taken as a signal amount S,floor noise without the peak was integrated to obtain a noise amount N,and a ratio S/N of the signal amount S to the noise amount N wasobtained as a signal-to-noise ratio (SNR). Next, the obtained SNR wasconverted into a relative value (dB) based on the SNR of ComparativeExample 1 as a reference medium. Next, using the SNR (dB) obtained asdescribed above, quality of an electromagnetic conversion characteristicwas determined as follows.

Better: The SNR of the magnetic tape is 1 dB or much better than the SNR(=0 (dB)) of the evaluation reference sample (Comparative Example 1).

Good: The SNR of the magnetic tape is equal to or exceeds the SNR (=0(dB) of the evaluation reference sample (Comparative Example 1)

Almost good: There is a portion where the SNR of the magnetic tape isless than the SNR (=0 (dB)) of the evaluation reference sample(Comparative Example 1).

Bad: The SNR of the magnetic tape is less than the SNR (=0 (dB)) of theevaluation reference sample (Comparative Example 1) over the entirearea.

(Evaluation of Winding Deviation)

First, a magnetic recording cartridge after the above-mentioned“determination of change amount of tape width” was prepared. Next, thereel around which the tape was wound was taken out from the magneticrecording cartridge, and an end face of the wound tape was visuallyobserved. Note that the reel has a flange, and at least one flange istransparent or translucent so that the internal tape winding can beobserved over the flange.

According to results of observation, in a case where the end face of thetape is not flat and there is a step or protrusion of the tape, the tapewas determined to have winding deviation. Furthermore, the “windingdeviation” is considered to be worse as a plurality of steps andprotrusions are observed. The above determination was made for eachsample. The winding deviation state of each sample was compared with thewinding deviation state of Comparative Example 1 as a reference medium,and the quality was determined as follows.

Good: In a case where the winding deviation state of the sample is equalto or less than the winding deviation state of the reference sample(comparative example 1)

Bad: In a case where the winding deviation state of the sample is largerthan the winding deviation state of the reference sample (comparativeexample 1)

(Evaluation of Winding State (Evaluation of the Presence or Absence ofWrinkles))

First, a magnetic recording cartridge after the above-mentioned“determination of change amount of tape width” was prepared. By visuallyobserving the winding state of the magnetic recording medium in themagnetic recording cartridge from the side with naked eyes, the presenceor absence of disorder of the winding state due to the occurrence ofwrinkles may be checked. In the observation, the winding state wasdetermined according to the following criteria.

Good: There is no disorder of the winding state caused by wrinkles.

Bad: There is disorder of the winding state caused by wrinkles.

Table 1 shows the configurations and evaluation results of the magnetictapes of Examples 1 to 26 and Comparative Examples 1 to 4.

TABLE 1 Base Thick- Δw β V Magnetic ness tT [ppm/ α [ppm/% σ_(MD) [mm/t_(m) Material [μm] [μm] N] [ppm/° C.] RH] ρ [M] min] [nm] AlignmentDegree Example 1 ε Iron Oxide 3.8 5.5 707 5.9 5.2 0.29 0.75 0.5 90Substantially Vertical Example 2 ε Iron Oxide 3.3 5.0 750 5.9 5.2 0.290.75 0.5 90 Substantially Vertical Example 3 ε Iron Oxide 3.2 4.5 8005.9 5.2 0.29 0.75 0.5 90 Substantially Vertical Example 4 ε Iron Oxide3.2 4.5 800 6 5 0.29 0.75 0.5 90 Substantially Vertical Example 5 ε IronOxide 3.2 4.5 800 8 5 0.29 0.75 0.5 90 Substantially Vertical Example 6ε Iron Oxide 3.2 4.6 800 6 3 0.29 0.75 0.5 90 Substantially VerticalExample 7 ε Iron Oxide 3.2 4.5 800 6 5 0.31 0.75 0.5 90 SubstantiallyVertical Example 8 ε Iron Oxide 3.2 4.5 800 6 5 0.35 0.75 0.5 90Substantially Vertical Example 9 ε Iron Oxide 3.2 4.5 800 6 5 0.31 0.80.5 90 Substantially Vertical Example 10 ε Iron Oxide 3.2 4.5 800 6 50.31 3.5 0.5 90 Substantially Vertical Example 11 ε Iron Oxide 3.2 4.5800 6 5 0.31 0.8 5 90 Substantially Vertical Example 12 ε Iron Oxide 3.24.4 800 6 5 0.31 0.75 0.5 40 Substantially Vertical Example 13CrPtCoSiO2 3.6 4.0 800 6 5 0.31 0.75 0.5 9 Vertical Example 14 ε IronOxide 3.2 4.4 800 6 5 0.31 0.75 0.5 90 Substantially Vertical Example 15ε Iron Oxide 3.2 4.5 800 6 5 0.31 0.75 0.5 90 Substantially VerticalExample 16 ε Iron Oxide 3.2 4.5 800 6 5 0.31 0.75 0.5 90 SubstantiallyVertical Example 17 ε Iron Oxide 3.2 4.5 800 6 5 0.31 0.75 0.5 90Substantially Vertical Example 18 ε Iron Oxide 3.2 4.5 800 6 5 0.31 0.750.5 110 Substantially Vertical Example 19 ε Iron Oxide 3.2 4.5 800 6 50.31 0.75 0.5 90 Substantially Vertical Example 20 ε Iron Oxide 3.2 4.5800 6 5 0.31 0.75 0.5 90 Substantially Vertical Example 21 ε Iron Oxide3.2 4.5 800 6 5 0.31 0.75 0.5 90 Substantially Vertical Example 22 εIron Oxide 3.2 4.5 800 6 5 0.31 0.75 0.5 90 Substantially VerticalExample 23 ε Iron Oxide 3.2 4.5 800 6 5 0.31 0.75 0.5 90 SubstantiallyVertical Example 24 ε Iron Oxide 3.2 4.5 800 6 5 0.31 5.0 0.5 90Substantially Vertical Example 25 Banum Ferrite 3.2 4.5 800 6 5 0.310.75 0.5 90 Substantially Vertical Example 26 ε Iron Oxide 3.8 5.5 700 65 0.29 0.75 0.5 90 Substantially Vertical Comparative ε Iron Oxide 3.85.5 650 5.9 5.2 0.29 0.75 0.5 90 Substantially Vertical Example 1Comparative ε Iron Oxide 3.6 5 800 5.9 5.2 0.29 0.75 0.5 90Substantially Vertical Example 2 Comparative ε Iron Oxide 3.6 5 800 5.95.2 0.29 0.75 0.5 90 Substantially Vertical Example 3 Comparative ε IronOxide 3.2 4.5 800 6 5 0.29 0.75 0.5 90 Non-aligned Example 4 T_(in)W −Electromagnetic State S2 t_(b) R_(ab) T_(out)W T_(in)W T_(out)WConversion Winding (Occurrence [%] [μm] [nm] μ [um] [um] [um]Determination Characteristic Deviation of Wrinkles) Example 1 65 0.6 60.50 0.13 0.20 0.07 4 Good Good Good Example 2 65 0.6 6 0.50 0.22 0.460.24 5 Good Good Good Example 3 65 0.3 6 0.50 0.25 0.50 0.25 6 Good GoodGood Example 4 65 0.3 6 0.50 0.25 0.50 0.25 7 Good Good Good Example 565 0.3 6 0.50 0.25 0.50 0.25 7 Good Good Good Example 6 65 0.3 6 0.500.25 0.50 0.25 8 Good Good Good Example 7 65 0.3 6 0.50 0.25 0.50 0.25 7Good Good Good Example 8 65 0.3 6 0.50 0.25 0.50 0.25 7 Good Good GoodExample 9 65 0.3 6 0.50 0.25 0.50 0.25 8 Good Good Good Example 10 650.3 6 0.50 0.25 0.50 0.25 8 Good Good Good Example 11 65 0.3 6 0.50 0.250.50 0.25 8 Good Good Good Example 12 65 0.3 6 0.50 0.22 0.42 0.20 7Good Good Good Example 13 98 0.3 6 0.50 0.15 0.20 0.05 7 Good Good GoodExample 14 65 0.2 6 0.50 0.25 0.50 0.25 7 Good Good Good Example 15 650.3 3 0.50 0.25 0.50 0.25 7 Good Good Good Example 16 65 0.3 6 0.20 0.250.50 0.25 7 Good Good Good Example 17 65 0.3 3 0.80 0.25 0.50 0.25 7Good Good Good Example 18 65 0.3 6 0.50 0.25 0.50 0.25 7 ApproximatelyGood Good Good Example 19 65 0.3 7 0.50 0.25 0.50 0.25 7 ApproximatelyGood Good Good Example 20 65 0.3 6 0.18 0.25 0.50 0.25 7 Good Bad GoodExample 21 65 0.3 6 0.82 0.25 0.50 0.25 7 Good Bad Good Example 22 730.3 6 0.50 0.25 0.50 0.25 8 Good Good Good Example 23 80 0.3 6 0.50 0.250.50 0.25 8 Better Good Good Example 24 65 0.3 6 0.50 0.25 0.50 0.25 8Good Good Good Example 25 65 0.3 6 0.50 0.25 0.50 0.25 7 Good Good GoodExample 26 65 0.6 6 0.50 −0.03 −0.02 0.01 7 Good Bad Good Comparative 650.6 6 0.50 0.14 0.22 0.08 1 Good Good Good Example 1 Comparative 65 0.66 0.50 0.25 0.22 −0.03 5 Good Good Bad Example 2 Comparative 65 0.6 60.50 −0.03 −0.03 0.00 1 Good Good Bad Example 3 Comparative 60 0.3 60.50 0.25 0.50 0.25 7 Bad Good Good Example 4

Note that each symbol in Table 1 refers to the following measurementvalues.

tT: Thickness of magnetic tape (unit: μm)

Δw: Dimension change amount in the width direction of the magnetic tapewith respect to a change in tension in the longitudinal direction of themagnetic tape (unit: ppm/N)

α: Thermal expansion coefficient of magnetic tape (unit: ppm/° C.)

β: Humidity expansion coefficient of magnetic tape (unit: ppm/% RH)

ρ: Poisson's ratio of magnetic tape

σ_(MD): Elastic limit value in the longitudinal direction of magnetictape (unit: N)

V: Speed for measuring elastic limit (unit: mm/min)

t_(m): Average thickness of magnetic layer (unit: nm)

S2: Squareness ratio (unit: %) in the thickness direction (verticaldirection) of the magnetic tape (unit: %)

tb: Average thickness of back layer (unit: μm)

Rab: Surface roughness of back layer (unit: nm)

μ: friction coefficient between magnetic surface and back surface

T_(in)W: Deviation amount of servo track width on the inner side of thewinding (unit: μm)

T_(out)W: Deviation amount of servo track width on the outer side of thewinding (unit: μm)

T_(in)W−T_(out)W: (Deviation amount of servo track width on inner sideof winding)−(Deviation amount of servo track width on outer side ofwinding) (unit: μm). The difference between the servo track widths onthe inner side of the winding and the outer side of the winding.

From the results shown in Table 1, the following can be seen.

In all of the magnetic tapes of Examples 1 to 26, the determinationresults of the change amount in tape width before and after storage was4 or more. (In other words, the deviation from the ideal of the“effective change amount of tape width” is small). Therefore, it can beseen that the magnetic recording cartridge according to the embodimentof the present technology is suitable for use in a recording andreproducing apparatus for adjusting tension in the longitudinaldirection.

From the results of the determination of the change amounts of tapewidths of Examples 1 to 26 and Comparative Example 1, it can be seenthat the dimensional change amount Δw of the magnetic recording tape is660 ppm/N or more, more preferably 700 ppm/N or more, even morepreferably 750 ppm/N, still more preferably 800 ppm/N or more, and thus,the magnetic recording tape is more suitable for use in the recordingand reproducing apparatus for adjusting tension in the longitudinaldirection (in particular, adjustment of the tape width by adjustingtension).

From the comparison of Examples 1 to 26 and Comparative Examples 2 and3, it can be seen that the difference in the servo track width betweenthe inner side and outer side of the winding is greater than 0.00preferably 0.01 μm or more, more preferably 0.02 μm or more, still morepreferably 0.05 and thus, the winding state is good (wrinkles do notoccur in a case where the magnetic recording tape is wound around thereel in the cartridge).

From the comparison of the evaluation results of Examples 3 to 6 and thelike, the thermal expansion coefficient α is preferably 5.9 ppm/° C.≤α≤8ppm/° C. from the viewpoint of suppressing the deviation from the idealof the “effective change amount of tape width”. Furthermore, from thecomparison of the evaluation results of Examples 3 to 6 and the like, itcan be seen that the humidity expansion coefficient β is preferably β≤5ppm/% RH from the viewpoint of suppressing the deviation from the idealof the “effective change amount of tape width”.

From the comparison of the evaluation results of Examples 7, 9, 10, andthe like, it can be seen that the elastic limit value σ_(MD) in thelongitudinal direction is 0.8 N≤σ_(MD) from the viewpoint of suppressingthe deviation from the ideal of the “effective change amount of tapewidth”.

From the comparison of Examples 9 and 11, it can be seen that theelastic limit value GMD does not depend on the speed V when the elasticlimit measurement is performed.

From the comparison of the evaluation results of Examples 7 and 18, itcan be seen that the thickness of the magnetic layer is preferably 100nm or less, particularly 90 nm or less, from the viewpoint of improvingelectromagnetic conversion characteristic.

From the comparison of the evaluation results of Examples 7, 15, 17 and19, it can be seen that the surface roughness R_(ab) of the back layeris preferably 3.0 nm≤R_(ab)≤7.5 nm from the viewpoint of improvingelectromagnetic conversion characteristic.

When the evaluation results of Examples 7, 16, 17, 20, and 21 arecompared with each other, the friction coefficient μ is 0.18<μ<0.82,particularly 0.20≤μ≤0.80, more particularly, 0.20≤μ≤0.78, and still moreparticularly, 0.25≤μ≤0.75, from the viewpoint of suppressing windingdeviation.

When Examples 1 to 26 and Comparative Example 4 are compared with eachother, it is preferable that the magnetic layer is aligned vertically orsubstantially vertically, from the viewpoint of improving theelectromagnetic conversion characteristic. Furthermore, from thecomparison of the evaluation results of Examples 7, 22, and 23, it canbe seen that the squareness ratio S2 of the magnetic tape in thevertical direction is preferably 73% or more, and particularly 80% ormore, from the viewpoint of improving electromagnetic conversioncharacteristic.

From the comparison of the evaluation results of Examples 7 and 25 orthe like, it can be seen that evaluation results similar to thoseobtained using ε iron oxide nanoparticles as magnetic particles can beobtained even in a case where the barium ferrite nanoparticles are usedas magnetic particles.

From the comparison of the results of Example 13 and other Examples, itcan be seen that evaluation results similar to those of the coating typemagnetic recording tape can be obtained even with the vacuum thin filmtype (sputter type) magnetic recording tape is used.

From the comparison of Example 1 and Example 26, it is considered thatthe occurrence of winding deviation is prevented because both the servotrack width on the inner side of the winding and the servo track widthon the outer side of the winding are wider than the servo lead headwidth. The magnetic tape in which both the servo track width on theinner side of the winding and the servo track width on the outer side ofthe winding is wider than the servo lead head width has a servo trackwidth larger than a servo lead head width over the entire length.Therefore, it is considered that the winding state is better because theservo rack width is larger than the servo lead head width over theentire length of the magnetic tape.

Although the embodiments and examples of the present technology havebeen specifically described above, the present technology is not limitedto the above-described embodiments and examples, and variousmodifications may be made on the basis of the technical idea of thepresent technology.

For example, the configurations, methods, steps, shapes, materials, andnumerical values or the like in the above embodiments and examples aremerely examples, and a configuration, a method, a step, a shape, amaterial and a numerical value or the like different therefrom may alsobe used. Furthermore, the chemical formulas of the compounds and thelike are typical, and are not limited to the mentioned valences in caseof the generic name of the same compound.

Furthermore, the configurations, methods, steps, shapes, materials, andnumerical values or the like of the above-described embodiments andexamples may be combined without departing from the spirit of thepresent technology.

Furthermore, in this specification, the numerical value range indicatedby “to” indicates the range including the numerical values mentionedbefore and after “to” as the minimum value and the maximum value,respectively. In the numerical range mentioned stepwise in thisspecification, the upper or lower limit of the numerical range of acertain stage may be replaced with the upper or lower limit of thenumerical range of the other stage. The materials exemplified in thisspecification can be used alone or in combination of two or more, unlessotherwise specified.

Note that the present technology can have the following configuration.

[1] A magnetic recording cartridge including

a magnetic recording medium of which

an average thickness t_(T) is t_(T)≤5.6 μm,

a dimensional change amount Δw in a width direction with respect to atension change in a longitudinal direction is 660 ppm/N≤Δw, and

a squareness ratio in a vertical direction is 65% or more,

in which the magnetic recording medium is accommodated in a state ofbeing wound around a reel and (a servo track width on an inner side ofwinding of the magnetic recording medium)−(a servo track width on anouter side of winding of the magnetic recording medium)>0 is satisfied.

[2] The magnetic recording cartridge described in [1], in which themagnetic recording medium has a servo track width larger than a servoread head width of a magnetic recording and reproducing apparatus inwhich the magnetic recording cartridge is loaded.

[3] The magnetic recording cartridge described in [2], in which themagnetic recording and reproducing apparatus is a timing servo typemagnetic recording and reproducing apparatus.

[4] The magnetic recording cartridge described in any one of [1] to [3],in which the dimensional change amount Δw is 700 ppm/N≤Δw.

[5] The magnetic recording cartridge described in any one of [1] to [3],in which the dimensional change amount Δw is 750 ppm/N≤Δw.

[6] The magnetic recording cartridge described in any one of [1] to [3],in which the dimensional change amount Δw is 800 ppm/N≤Δw.

[7] The magnetic recording cartridge described in any one of [1] to [6],in which the magnetic recording medium includes a back layer, and asurface roughness R_(ab) of the back layer is 3.0 nm≤R_(ab)≤7.5 nm.

[8] The magnetic recording cartridge described in any one of [1] to [7],in which the magnetic recording medium includes a magnetic layer and aback layer, and a friction coefficient μ between a surface on a side ofthe magnetic layer and a surface on a side of the back layer is0.20≤μ≤0.80.

[9] The magnetic recording cartridge described in any one of [1] to [8],in which a thermal expansion coefficient α of the magnetic recordingmedium is 5.5 ppm/° C.≤α≤9 ppm/° C. and a humidity expansion coefficientβ of the magnetic recording medium is β≤5.5 ppm/% RH.

[10] The magnetic recording cartridge described in any one of [1] to[9], in which a Poisson's ratio ρ of the magnetic recording medium is0.25≤ρ.

[11] The magnetic recording cartridge described in any one of [1] to[10], in which an elastic limit value α_(MD) of the magnetic recordingmedium in the longitudinal direction is 0.7≤≤σ_(MD).

[12] The magnetic recording cartridge described in [11], in which theelastic limit value σ_(MD) does not depend on a speed V when elasticlimit is measured.

[13] The magnetic recording cartridge described in any one of [1] to[12], in which the magnetic recording medium includes a magnetic layer,and the magnetic layer is vertically aligned.

[14] The magnetic recording cartridge described in any one of [1] to[13], in which the magnetic recording medium includes the back layer andan average thickness t_(b) of a back layer is t_(b)≤0.6 μm.

[15] The magnetic recording cartridge described in any one of [1] to[14], in which the magnetic recording medium includes a magnetic layer,and the magnetic layer is a sputtered layer.

[16] The magnetic recording cartridge described in [15], in which anaverage thickness t_(m) of the magnetic layer is 9 nm≤t_(m)≤90 nm.

[17] The magnetic recording cartridge described in any one of [1] to[16], in which the magnetic recording medium includes a magnetic layer,and the magnetic layer contain magnetic powder.

[18] The magnetic recording cartridge described in [17], in which theaverage thickness t_(m) of the magnetic layer is 35 nm≤t_(m)≤120 nm.

[19] The magnetic recording cartridge described in [17] or [18], inwhich the magnetic powder includes ε iron oxide magnetic powder, bariumferrite magnetic powder, cobalt ferrite magnetic powder, or strontiumferrite magnetic powder.

[20] A magnetic recording cartridge including

a magnetic recording medium of which

an average thickness t_(T) is t_(T)≤5.6 μm,

a dimensional change amount Δw in a width direction with respect to achange in tension in a longitudinal direction is 660 ppm/N≤Δw, and

a squareness ratio in a vertical direction is 65% or more,

in which the magnetic recording medium has a servo track width largerthan a servo read head width of a magnetic recording and reproducingapparatus in which the magnetic recording cartridge is loaded.

REFERENCE SIGNS LIST

-   -   1 Magnetic recording cartridge    -   3 Reel    -   10 Magnetic recording medium    -   11 Base layer    -   12 Ground layer    -   13 Magnetic layer    -   14 Back layer

The invention claimed is:
 1. A magnetic recording cartridge comprising:a cartridge case, a reel, and a magnetic recording medium having amagnetic layer, a non-magnetic layer, a base layer and a back layer,wherein an average thickness of the magnetic recording medium t_(T) is3.5 μm≤t_(T)≤5.6 μm, a dimensional change amount Δw in a width directionof the magnetic recording medium with respect to a tension change in alongitudinal direction of the magnetic recording medium is 700ppm/N≤Δw≤20000 ppm, and the magnetic recording medium is accommodated ina state of being wound around the reel in the cartridge case and (aservo track width on an inner side of winding of the magnetic recordingmedium)−(a servo track width on an outer side of winding of the magneticrecording medium)>0 is satisfied.
 2. The magnetic recording cartridgeaccording to claim 1, wherein the dimensional change amount Δw in thewidth direction of the magnetic recording medium with respect to thetension change in the longitudinal direction of the magnetic recordingmedium is 750 ppm/N≤Δw≤20000 ppm.
 3. The magnetic recording cartridgeaccording to claim 1, wherein the dimensional change amount Δw in thewidth direction of the magnetic recording medium with respect to thetension change in the longitudinal direction of the magnetic recordingmedium is 800 ppm/N≤Δw≤20000 ppm.
 4. The magnetic recording cartridgeaccording to claim 1, wherein the average thickness of the magneticrecording medium t_(T) is 3.5 μm≤t_(T)≤5.3 μm.
 5. The magnetic recordingcartridge according to claim 1, wherein the average thickness of themagnetic recording medium t_(T) is 3.5 μm≤t_(T)≤5.2 μm.
 6. The magneticrecording cartridge according to claim 1, wherein an average thicknessof the magnetic layer t_(m) is 35 nm≤tm≤120 nm.
 7. The magneticrecording cartridge according to claim 1, wherein an average thicknessof the non-magnetic layer is 0.6 μm to 2.0 μm.
 8. The magnetic recordingcartridge according to claim 1, wherein an average thickness of the baselayer is 2.5 μm to 6 μm.
 9. The magnetic recording cartridge accordingto claim 1, wherein an average thickness of the base layer is 2.6 μm to5 μm.
 10. The magnetic recording cartridge according to claim 1, whereinan average thickness of the back layer t_(b) is t_(b)≤0.6 μm.
 11. Themagnetic recording cartridge according to claim 1, wherein 0.01 μm≤(theservo track width on an inner side of winding of the magnetic recordingmedium)−(the servo track width on an outer side of winding of themagnetic recording medium)≤2.5 μm is satisfied.
 12. The magneticrecording cartridge according to claim 1, wherein the magnetic layer hasmagnetic powder and a binder, and the magnetic powder includes one ormore of ε iron oxide magnetic powder, barium ferrite magnetic powder,cobalt ferrite magnetic powder, and strontium ferrite magnetic powder.13. The magnetic recording cartridge according to claim 12, wherein themagnetic powder includes the ε iron oxide magnetic powder, and a peakratio X/Y of a main peak height X and a height Y of a sub peak in thevicinity of magnetic field zero in a switching field distribution (SFD)curve of the magnetic recording medium is no less than 3.0 and no morethan
 100. 14. The magnetic recording cartridge according to claim 13,wherein an average particle size of the magnetic powder is no less than8 nm and no more than 22 nm.
 15. The magnetic recording cartridgeaccording to claim 12, wherein the magnetic powder includes the bariumferrite magnetic powder, an average thickness of the magnetic layert_(m) is 35 nm≤t_(m)≤100 nm, and a coercive force Hc of the magneticrecording medium measured in a vertical direction of the magneticrecording medium is 160 kA/m to 280 kA/m.
 16. The magnetic recordingcartridge according to claim 15, wherein an average particle size of themagnetic powder is no less than 12 nm and no more than 25 nm.
 17. Themagnetic recording cartridge according to claim 1, wherein a thermalexpansion coefficient α of the magnetic recording medium is 5.5 ppm/°C.≤α≤9 ppm/° C. and a humidity expansion coefficient β of the magneticrecording medium is β≤5.5 ppm/% RH.
 18. The magnetic recording cartridgeaccording to claim 1, wherein a surface roughness R_(ab) of the backlayer is 3.0 nm≤R_(ab)≤7.5 nm.
 19. The magnetic recording cartridgeaccording to claim 1, wherein a friction coefficient μ between a surfaceon a side of the magnetic layer and a surface on a side of the backlayer is 0.20≤μ≤0.80.
 20. The magnetic recording cartridge according toclaim 1, wherein a Poisson's ratio ρ of the magnetic recording medium is0.25≤ρ.
 21. The magnetic recording cartridge according to claim 1,wherein an elastic limit value σ_(MD) of the magnetic recording mediumin the longitudinal direction of the magnetic recording medium is 0.7N≤σ_(MD).
 22. The magnetic recording cartridge according to claim 21,wherein the elastic limit value σ_(MD) does not depend on a speed V whenan elastic limit is measured.
 23. The magnetic recording cartridgeaccording to claim 1, wherein the magnetic layer is vertically aligned.24. The magnetic recording cartridge according to claim 1, wherein aplurality of servo bands are formed in the magnetic layer and a numberof the servo bands is 3 to
 11. 25. The magnetic recording cartridgeaccording to claim 1, wherein the base layer includes a polyester resin.26. The magnetic recording cartridge according to claim 1, wherein asquareness ratio measured in a vertical direction of the magneticrecording medium is 65% or more.
 27. The magnetic recording cartridgeaccording to claim 1, wherein a squareness ratio measured in thevertical direction of the magnetic recording medium is 70% or more. 28.The magnetic recording cartridge according to claim 1, wherein asquareness ratio measured in the vertical direction of the magneticrecording medium is 73% or more.
 29. The magnetic recording cartridgeaccording to claim 1, wherein a coercive force Hc of the magneticrecording medium measured in a vertical direction of the magneticrecording medium is 220 kA/m to 310 kA/m.
 30. The magnetic recordingcartridge according to claim 1, wherein the magnetic layer has a bariumferrite magnetic powder and a binder, the base layer includes apolyester resin, an average particle size of the barium ferrite magneticpowder is 12 nm to 25 nm, an average thickness of the magnetic layert_(m) is 35 nm≤t_(m)≤100 nm, an average thickness of the non-magneticlayer is 0.6 μm to 2.0 μm, an average thickness of the base layer is 2.5μm to 6 μm, an average thickness of the back layer t_(b) is t_(b)≤0.6μm, a surface roughness R_(ab) of the back layer is 3.0 nm≤R_(ab)≤7.5nm, a coercive force Hc of the magnetic recording medium measured in avertical direction of the magnetic recording medium is 160 kA/m to 280kA/m, and a squareness ratio measured in a vertical direction of themagnetic recording medium is 65% or more.